A network is a group of computers and other devices, such as printers
and modems, connected to each other. This enables the computers to effectively share data and resources. The concept of sharing resources over a network is called networking. The computers in a network can share data, messages, graphics, printers, fax machines, modems, and other hardware and   software resources.
In a Peer-to-Peer Network, there are no dedicated servers, and there is  no hierarchy among the computers. All the computers are equal and therefore  are known as peers. Each computer functions as both a client and a server.
And there is no administrator responsible for the entire network. The user at   each computer determines what data on that computer is shared on the network. In a peer-to-peer network, all computers are considered equal; they all have
the same abilities to use the resources available on the network. Computers are not dedicated to function as servers. They use the network to share resources among the independent peers. The computer whose applications are required by the other networked computers functions as a server. The other computers function
as clients. Therefore, a dedicated administrator is not assigned for network
management. A peer-to-peer network is a small group of people using a network and performing similar tasks, which necessitates the sharing of resources.
The users of each computer plan and control the security of their resources.  The users determine the resources on their computers, which can be shared on  the network. The shared network resources, such as disk space, printers or faxes, can be used by anyone who has access to the network. This is possible only   if the shared network resources are not password protected. A peer-to-peer network does not support a central login process. Peer-to-peer networks are relatively simple. The users handle administration.
A dedicated server is one that functions only as a server and is not used as a client or workstation. Server Based Networks have become the standard models for networking. In a server-based network, clients rely on the services that the server provides, such as file storing and printing.
Client computers are generally less powerful than server computers. A server-based network using network operating system is that the networks are organized into domains. In server-based networks, a network administrator centrally manages the resource security. The administrator defines and manages user access to network resources.
Local Area Network (LAN) is a network with two or   more computers connected to each other in a single location.
Wired Local Area Network is the simplest type of network in which computers are connected to each other by cables.
Each of the computers on the LAN is also called a node. A LAN is characterized by three primary attributes: topology, medium, protocols. Wireless local-area networks have the advantage of expandability. The   topology and the medium used on a particular network are specified by the protocol.
There are a number of ways in which nodes can communicate over a network. The simplest is to establish a dedicated link between the transmitting and receiving stations. This technique is known as circuit switching. A better way of communicating is to use a technique known as packet switching, in which a dedicated path is not reserved between the source and the destination.
Wireless Local Area Network refers to technology that enables two or more computers to communicate using standard network protocols, but without network cabling. Each computer can communicate directly with all of the other wireless enabled computers. A wireless network can also use an access point, or base station. In this type of network the access point acts like a hub, providing connectivity for the wireless computers. It can connect the wireless LAN to a wired LAN, allowing wireless computer access to LAN resources, such as file servers or existing Internet Connectivity.

There are two types of access points:
Hardware access points (HAP) offer complete support of most wireless features, but check your requirements carefully.
Software Access Points which run on a computer equipped with a wireless network interface card as used in peer-to-peer wireless network. The software routers that can be used as a basic Software Access Point, and include features not commonly found in hardware solutions.
Wireless networking offers a costeffective solution to users with difficult physical installations such as campuses, hospitals or businesses with more than one location in immediate proximity but separated by public thoroughfare. This type of installation requires two access points. Each access point acts as a bridge or router connecting its own LAN to the wireless connection. The wireless connection allows the two access points to communicate with each other, and therefore interconnect the two LAN's. Each access point has a finite range within which a wireless connection can be maintained between the client computer and the access point. The actual distance varies depending upon the environment. Also it should be noted that when operating at the limits of range the performance may drop, as the quality of connection deteriorates and the system compensates. Typical indoor ranges are 150-300 feet, but can be shorter if the building construction interferes with radio transmissions. Longer ranges are possible, but performance will degrade with distance. Outdoor ranges are quoted up to 1000 feet, but again this depends upon the environment.
In most cases, separate access points are interconnected via a wired LAN, providing wireless connectivity in specific areas such as offices or rooms, but connected to a main wired LAN for access to network resources, such as file servers. If a single area is too large to be covered by a single access point, then multiple access   points or extension points can be used.
When using multiple access points, each access point wireless area should overlap its neighbors. This provides a seamless area for users to move around in using a feature called "roaming." A wireless computer can "roam" from one access point to another, with the software and hardware maintaining a steady network connection by monitoring the signal strength from in-range access points and locking on to the one with the best quality.
Some access point configurations require security authentication when swapping access points, usually in the form of a password dialog box. Access points are required to have overlapping wireless areas to achieve this. A user can move from Area 1 to Area 2 transparently. The Wireless networking hardware automatically swaps to the Access Point with the best signal.
Some manufacturers produce extension points, which act as wireless relays, extending the range of a single access point. Multiple extension points can be strung together to provide wireless access to far away locations from the central access point. To share an Internet connection across a LAN you need two things: an Internet sharing hardware device or software program and a LAN. Any computer equipped with a wireless network card running suitable Internet sharing software can be used as a software access point. A number of vendors offer hardware access points.
A hardware access point may provide Internet Sharing capabilities to Wired LAN computers, but does not usually provide much flexibility beyond very simple configurations.
If an existing wired LAN already has an Internet connection, then the hardware access points simply connect to LAN and allow wireless computers to access the existing Internet connection in the same way as wired LAN computers.
Wireless communications obviously provide potential security issues, as an intruder does not need physical access to the traditional wired network in order to gain access to data communications. However, 802.11 wireless communications cannot be received much less decoded by simple scanners, short wave receivers etc. This has led to the common misconception that wireless communications cannot be eavesdropped at
all. However, eavesdropping is possible using specialist equipment.
To protect against any potential security issues, 802.11 wireless communications have a function called WEP. Wireless networking hardware requires the use of underlying technology that deals with radio frequencies as well as data transmission. The most widely used standard is 802.11 produced by the Institute
of Electrical and Electronic Engineers (IEEE). This is a standard defining all aspects of Radio Frequency Wireless networking.
It should also be noted that traditional Virtual Private Networking (VPN)   techniques will work over wireless networks in the same way as traditional wired   networks.