A mitre saw is a precision saw that people use to make accurate crosscuts and, as the name implies, mitres in wood. It's suspended on a guide that lets the user cut with precision and accuracy. While manual mitre saws still exist, most mitre saws today are power tools.
Mitre saws come with the saw itself and also bevels and frames to hold and guide the operation, as the saw makes precise cuts in wood. Cut straight with a mitre saw.