By circular machine you probably mean a circular saw - one of the most common power tools.
Circular saw is a power tool that uses a toothed or abrasive disc/ blade rotating at high speed to cut material.
Key parts:
Circular blade: 4" to 16"+ diameter. Teeth type depends on material - wood, metal, masonry
Motor: Corded or cordless battery. Drives the blade at 3000-6000 RPM
Base plate/shoe: Flat plate that rides on the material for stable, straight cuts
Depth & bevel adjustment: Set how deep to cut and angle from 0-45°
Main types:
Handheld circular saw: Portable, used for framing, plywood, general construction
Table saw: Blade mounted under a table, material pushed through. High accuracy for ripping
Miter saw: Blade pivots down onto material. For accurate crosscuts and miters in trim/ molding
Cut-off saw/ chop saw: Abrasive disc