I heard in a day, about 20 pushups will help to build muscles, if we do more then that, then it will help only for the strength & endurance, is this correct ?
Unless youre adding weight plates to your back, then there is hardly any progressive overload in terms of hypertrophy or strength that you can you. whats the maximum number of pushups you can do? is it 20?
Here are rep ranges to build hypertrophy, etc..
6-8: mostly strength + some hypertrophy
12-15: some hypertrophy with mostly endurance
with 20 pushups being your maximum then you can build endurance based off the above chart. now youve gone up to 25 pushups, youre still building more muscular endurance. Now anything after 25 is more likely to just build cardio or lactic energy system.. which is better done with bodyweight circuits for high intensity interval training, or just simply taking a jog than doing more and more pushups everyday.
To answer your question it would only build endurance and only until your body adapted to doing those. if you can only do 4 or 5 pushups then yes you are building strength, then muscle at 10, etc..
you can add weight to your back to make these harder once youve hit 30(unless your doing pushups for cardio, etc..).
if youre trying to build strength, a dumbbell bench press is more back friendly and more result-worthy if strength is your focus.