However, wireless networking is far behind wired networking in terms of bandwidth and throughput, so the existing wired networks remain, and there's a need to bridge the two. Enter the wireless access point: a network device that repeats a network signal over it's assigned radio spectrum, and vice versa. A cable goes in one end, and an antenna in the other; the effect is to create a seamless transition between wired and wireless devices.
A typical corporate use will be to attach a wireless access point to the wired network, and provide wireless client adapters for users who need them. Within the range of the access point, the wireless end-user has a full network connection with the benefit of mobility. In this instance, the access point is a gateway for clients to access the network. Another use is to bridge two wired networks where cable is not appropriate; for example, a manufacturer can connect a remote warehouse (within line of sight) by radio, with a wired network in each facility.
Another topography is called a lily pad network: a series of access points spread over a large area, each connected to a different network, providing 'hot spots' where a wireless client can connect to the Internet without regard for the particular networks to which it's attached at the moment. The concept is somewhat accidental in large cities, where a combination of coffee shops, libraries, and other public spaces offering wireless access points allow wireless clients to roam over a large area (i.e., hopping from lily pad to lily pad), staying more or less continually connected.
Wireless access points have a limited range, but multiple access points can act as repeaters for a root node, extending the range of wireless coverage for a single access point.