This post will describe 802.11 security basics which you should know for the CWNA exam.
Authentication is the verification of a device/user. This can be handled by usernames & passwords or certificates.
Authorization is the verification if the users/device is allowed to have access to the requested resources (network). This can be restricted to device, location or time of day.
Accounting tracks the usage of the resources being used. Records are being maintained of which user access what resource. This accounting trail is needed by some regulations (PCI).