A chop saw is a type of saw that is generally meant for cutting raw stock down to the approximately correct size. Some of these saws are meant for wood, while others are meant for cutting metal to size. Usually you clamp or otherwise hold your workpiece in place, and then the circular blade rotates down to cut through the material. Often they have blade protector so that the dangerous spinning blade is almost exposed for as little time as possible while cutting through the material.
Some chop saws are mounted on the bench, while others are portable and are meant for use at the job site. It's important to remember that chop saws are generally meant for less precise cuts and that finish work is done on a more precise saw.
Angle Saw
A common use is for cutting wooden 2 by 4s down to size for a deck, or cutting up metal pipe. It's important to remember that a saw for metal and one for wood can generally look similar, but they work differently and the blades will look a lot different too. Wood is generally cut through with a toothed blade, while metal is usually ground through with an abrasive blade. The wood will make saw dust, while the metal yields sparks! Be sure to use the appropriate saw and blade with the right material! Using the wrong one may have unpredictable consequences that you never want to experience. Battery powered chop saws are now available but these may not provide enough sustained power for big jobs.