Q: How much time is required for muscles to recover?What happens if u make weight training again before that time passes?

A: Recovery time will depend on the intensity and duration of the workout as well as the diet. After a good weighttraining session you should wait at least 2 days to train the same muscles again and you could easily wait a whole week. In fact many routines are structured to work each muscle group only once a week. These are called 'split' routines as opposed to 'whole-body' routines which work all the muscles 2-3 times per week. You can find samples of both in my Weighttraining article. Both types of routines are perfectly fine and switching between them can provide extra variety which is always good.

If you always train too soon, before muscles have recovered, you will eventually overtrain which will result in injuries and/or lack of progress. Overtraining is extremely common, so if in doubt, do LESS. The quality of your workouts is much more important than their length.