Weight training involves using some type of resistance to do a variety of exercises designed to challenge all your muscle groups, including your chest, back, shoulder, biceps, triceps, core, and lower body.
The idea is that, when you use more resistance than your body normally handles, your muscles get stronger, along with your bones and connective tissue, all while building lean muscle tissue. That lean muscle tissue is more metabolically active than fat, which means you burn more calories all day long, even when you’re not exercising.
Weight training doesn’t mean you have to use things like dumbbells or machines, although those work. Anything that provides resistance can do the job—resistance bands, barbells, a heavy backpack, or, if you’re a beginner, your own body weight might be enough to get you started.