Exercise movements can be broken down into compound and isolation exercises. The difference between the two is the number of joints and the number of muscle groups used to complete the movement.
Isolation movements involve using one joint and muscle group. These types of movements are good for strengthening specific muscle groups. Working on specific muscle groups can help improve any weaknesses that may be present when performing compound lifts. Isolation exercises consist of leg extensions, bicep curls and tricep extensions.
Compound movements involve using multiple joints and multiple muscle groups in one movement. These types of movements involve a large amount of muscle being worked. So it is good for improving general strength, developing a base strength and mobility. Compound exercises consist of squats, deadlifts, bench press and pull ups.
When you are performing a squat, you will be engaging your quads, glutes, core, back and calves. This movement will not only increase your strength but also mobility when it comes to daily tasks such as how easily you are able to get off the ground etc.
For beginners it is best to focus mostly on compound movements so you can build up your base strength and mobility before going on to focus on specific muscles.
Love the journey, J.