AP (Access point) mode: will allow you to add wireless access to en existing router or switch. Using the DAP-1522/1555 with an existing wireless router will allow you to disable the AP of the router and use 802.11n(draft) wireless speeds of the DAP-1522/1555 on your network.

Bridge mode: will allow you to connect two or more networks or network devices separated physically to each other wirelessly to make a connection, operating on the 802.11 standard.