camera technique

[Paris_Hilton]

i cant quite find the right terminology for this, but basically i was just wondering if anyone knew what that technique is called when taking a photo, where the lens turns circular, and it kinda looks like your looking in a fishbowl? its quite confusing to describe, but i hope someone knows what im going on about! also, ive got a Nikon Coolpix, so as a bonus if anyone knows how to turn it on with this camera, that would be great! thank you x