A chainsaw consists of a two-stroke engine that rotates a chain of blades. The first chainsaw was made in 1830 by the German inventor Bernard Heine. It was originally called the "osteotome" and was used to cut bone. Andreas Stihl was the first to patent the gas-powered chainsaw. He created a company to mass produce them in 1927, a company that still exists.
The chainsaw has several components: an engine, drive mechanism, guide bar and cutting chain. The engine itself consists of a cylinder, piston, connecting rod, crankshaft, carburetor and magneto. Of course, it is also made up of a frame that includes all these parts, a trigger and a handle.
The chain is driven by the clutch. When the clutch is engaged, the chain will move. When the engine is idling it won't move. The clutch is controlled by a trigger on the handle. The chain revolves around the guide bar, which is attached to the frame. The chain is made up of several small blades, called teeth, that are linked to each other. The teeth may not be significantly sharp, but they cut very well when they move at the proper speed. The teeth that make up the chain need to be small, otherwise the chain could often get stuck.
A spark plug fires once every revolution in a two-stroke engine. This gives it significant power for use in a hand-held machine. When the engine fires it moves the piston. The piston is what moves the crankshaft. The piston moves up and down which makes the crankshaft rotate. The crankshaft is what moves and rotates the clutch. The chain is attached to the clutch, so when the clutch rotates, the chain rotates around the guide bar. A small oil pump is used keep the chain lubricated while it moves around the clutch.