Children can be clumsy. Some of it is very natural. As they're learning to walk and climb and run and do all these things, it's possible that they may trip and fall and that's just how they learn; you fall and you get right back up again.
It can be that there is something else going on, but you have to take things with a grain of salt. Is it that every day they're stumbling into things? Is it that every are they bumping into things and they're falling and they're not looking where they're going? Are they running looking in this direction, not straight ahead? What's going on? The most important thing to do is observe your child. Observe and take note. When are they falling? How are they falling? What's going on?
Could it be that they're tripping on the same leg? And perhaps one side is weaker than the other. Perhaps they're having difficulty walking. Perhaps it requires intervention. Observe, take note and take that information and share that information with your child's pediatrician who will then be able to direct you accordingly.