The major muscle groups are the legs, arms, chest, back and abs. Each muscle has a unique function and they coherently allow day to day activities. When you work out a muscle group properly, it is possible to feel muscles and joints that you didn’t even know were there. Some people choose to work out a muscle group exclusively one day, and move on to a muscle group that is not related the next day. This is to give the muscle groups each a rest. If you work out a muscle group properly, you should feel sore. If you don’t feel sore, then you probably didn’t use enough weight or didn’t do enough repetitions.
It is very imperative to have proper workout routines when working out. If you are going through the motions, and not working out a muscle properly, then your work is in vain. When working out a muscle group, some people use spotters or trainers to help them use the muscles properly.