CIRCUIT SWITCHING - Receiver is contacted to check they are ready to receive some data. If OK then connections are established between network segments, connecting the sender and the receiver up. Once the data has been transmitted then the temporary circuits connections are removed. This was generally used in the telephone networks, before they became digitised.
PACKET SWITCHING - Data is wrapped into packets of data before sending
Connectionless - The packet is sent blindly across the network, whether or not the recipient is ready
Connection-orientated - Acknowledgement request is sent with the first packet of data. If acknowledgement is received, only then does the sender, send the packets onto the network.