Compact cameras and Ultra Compact cameras are designed to be small enough the fit into your pocket. They are also called “Point-and-shoot” cameras and are mainly used for snapshot photography.

Ultra Compact cameras are the smallest standard cameras available.

Kodak EasyShare M381
12.0mp
35-175mm (5x) zoom lens

Compact Cameras are still small, but tend to be bulkier than ultra compact cameras and often have better features.

Canon PowerShot A580
8mp
35-140mm (4x) zoom lens

SLR-like Cameras
These are large cameras which look like SLR cameras, but lack the single-lens reflex (see DSLR for definition). They have smaller sensors compared to the DSLR and the lenses are not removable, making the photographer unable to create desired affects with different lenses.

Nikon Coolpix P90
12.1mp
26-624mm (24x) zoom lens

DSLR Cameras
Digital single-lens reflex cameras (DSLRs) are digital cameras based on film single-lens reflex cameras (SLRs). They take their name from their unique viewing system, in which a mirror reflects light from the lens through a separate optical viewfinder. In order to capture an image the mirror is flipped out of the way, allowing light to fall on the imager. Since no light reaches the imager during framing, autofocus is accomplished using specialized sensors in the mirror box itself. From wikipedia.com

Canon EOS 5D MarkII
21.0mp