Dear Mai Nguyen
Toes are fairly important for humans. They help us to balance and they give us a bit of leverage when we are walking and running.
Toes were much more important for our 'ancestors'. They needed them for balance, holding on to things and for manipulating things. Toenails used to be claws--so they would have been helpful for defence and attack.
People who have lost their toes usually get along fairly well without them. But people who have no arms find their toes useful for all sorts of things...even for playing the piano.