Resistance training is any form of exercise that forces your skeletal muscles (not involuntary muscles like your heart, lungs, etc.) to contract. In these exercises, an external resistance (such as a weight or gravity) is used to induce contractions, and those contractions lead to increased muscle mass, strength, endurance, and strength.
What can you use for that external resistance?
Anything you want! You can use dumbbells, kettlebells, barbells, resistance bands, your body weight, water bottles, bricks, anything you can think of. As long as this heavy object causes muscle contractions, your workout is considered resistance training.

Types of resistance exercises:

There are three main types of posture exercises:
1. body weight
This type of exercise uses only your body weight to force your muscles to contract. This type of exercise includes exercises such as barfix, Swedish swimming, and squats.
2. Free weights
Using dumbbells, barbells and kettlebells helps to increase the pressure on your muscles and causes contraction and muscle building. Free weight training is the most effective form of resistance training because it engages the secondary (stabilizing) muscles, leading to more effective muscle growth.
3. Devices
Each club has dozens of devices. The pec deck machine, cable machine, front leg machine, etc. machines are not as effective as free weights, but they are a safer alternative for people who are new to resistance training.