An Access Control List (ACL) is a general idea with a variety of specific applications in areas such as operating systems, application security, or networking.
For Windows products, ACLs are used to manage user permissions to objects such as files and registry keys. Windows Server features two types of ACL, discretionary ACL (DACL) and system access ACL (SACL). [1]
In the area of routing, Cisco uses the concept of ACL in reference to firewall-like packet inspection. The table below lists some of the different ACL types available in Cisco IOS and gives a brief description of the services provided by each type of ACL.
Classic Cisco ACLs are applied on a per-interface basis. These ACLs can be applied to the interface in either an inbound or outbound direction. [2] More recently, Cisco has introduced an approach called Zone-Based Policy Firewall that allows for aggregation of multiple interfaces into unified security policy zones. [3] Vyatta is a another routing product that also features both per-interface and zone-based firewall rules. [4]
References:
[1] http://msdn.microsoft.com/en-us/library/windows/desktop/aa374872(v=vs.85).aspx
[2] http://www.cisco.com/en/US/docs/ios/11_3/security/configuration/guide/scacls.html
[3] http://www.cisco.com/en/US/products/ps6441/products_feature_guide09186a008060f6dd.html#wp1063104