Your AP may have two radio/antenna combinations, in 2.4G and 5G radio bands. You can advertise up to 8 SSIDs on each radio, but less than 5 is recommended.
The APs do not interfere with themselves, but use time division multiplexing
methods to share the bandwidth among the wireless clients using your SSIDs.
http://en.wikipedia.org/wiki/802.11
Investigate CWNA (Certified Wireless Network Administrator) training online for
better understanding.