Client Association: A user's notebook computer or other device connects to an Access Point and an Ethernet-like wireless link is formed. The idea of an "Ethernet-like" link refers to the fact that once the client machine has connected ("associated") to an Access Point then the transfer of data occurs just as if the client device were attached to an Ethernet cable (i.e.: DHCP, IP, TCP, UDP, and behaviors consistent with a normal Ethernet connection).
Access Point: A central radio to which client devices associate to form wireless links. Multiple Access Points can communicate to each other through a matrix of connectivity called the Distribution System. The Distribution System is necessary so that an aggregate of Access Points can operate as if they were one, single Local Area Network (which is to say, a single IP subnet and broadcast domain).
Distribution System: The interconnection between access points allowing clients to roam within a particular area and remain constantly connected to the network with the same IP address. Typically the distribution system is a wired Ethernet network where the access points are wired back to a central Ethernet switch. The distribution system can, however, consist of RF connections between Access Points. The entire Distribution System acts as a single Layer 2 broadcast domain and a single IP subnet. A client device can roam anywhere in the Distribution System and be handed off from one Access Point to another automatically (as per the rules of 802.11), retaining the same IP address and remaining part of the same network as they roam.
Wired Distribution System: The Access Points are wired with Ethernet cable to one or more Ethernet switches. The Distribution System for communication between Access Points is based on wired Ethernet. Note that both a wired, and wireless Distribution System is also the portal through which clients access the Internet or other back-end file servers or resources. A broadband modem or other Internet connection attaches to the Distribution System through a router or HotSpot access controller gateway. So, whether the Distribution System is wired, or wireless, there will always be some type of Portal connection OUT of the Distribution System to the rest of the world.
Wireless Distribution System: When Access Points are manually configured so that they're interconnected using radio links (as opposed to Ethernet cables) a Wireless Distribution System (WDS)is formed. In essence, the WDS is a matrix of Access Point to Access Point links. Each of the links is manually configured by the network administrator so each Access Point knows the address of its peers in the connectivity matrix. The Distribution System between Access Points is based on wireless communication links.
Mesh Router System: When Access Points are designed to automatically discover their peers and automatically create a matrix of Access Point to Access Point communication links, a Mesh Router system is formed. With regard to the functionality of the mesh, it serves the same purpose as WDS: to connect Access Points to each other. The fundamental difference between WDS and Mesh Routing is the automatic discovery and configuration mechanism in a Mesh Router which also makes the Mesh Router fault tolerant. If a Mesh Router link were to fail, the mesh would attempt to find an alternative path around the failed section. If a WDS link fails there is no fail-over mechanism provided.