There are several different types of power saws used in building including the circular, reciprocating, saber and chain saws. Each saw is suited for a different set of tasks.
A circular saw has a circular blade and cuts by spinning. The teeth of the blade varies by the cut you wish to make (with the grain, across the grain, or to cut non-wood materials). Circular saws are used mostly to cut lumber but there are special blades that can cut other types of material including glass, cement, and fabric. There are two types of portable circular saws: side-drive and worm-drive. The side-drive saw has the handle and trigger above the saw while the worm drive has the handle and trigger on the side.
Circular Saw. Image courtesy of Lowes.com
A chain saw can cut heavy timber. A chain saw cuts by a saw chain that moves quickly around a guide bar. Unlike the other saws in this article, a chain saw is usually powered by gasoline although electric chain saws do exist.
Chain Saw. Image Courtesy of Lowes.com
A reciprocating saw blade looks like a small handsaw and cuts by moving up and down. It can cut out sections of framing and do other tasks that would not be practical with a circular saw making it very useful for remodeling work.
Reciprocating Saw. Image Courtesy of Lowes.com
A saber saw (a.k.a. jig saw) has a long blade that moves in a circular (not spinning) motion cutting the material on the upstroke. The saber saw is used to cut thin materials and can cut non-linear patterns.
Saber saw or Jigsaw. Image Courtesy of Lowes.com
- Koel, Leonard: Carpentry, Third Edition. Copyright 1997 by American Technical Publishers, Inc.
Images source: http://www.lowes.com