Belonging to the leaf beetle family it is often seen, yes you guess right, on leaves feeding. They are small beetles and if not for their often bright attractive colors it would be difficult to spot them.
Observing them closer you will notice that their hindlegs are bigger which helps them to jump like a flea, hence the name Flea beetles.
Sometimes they are regarded as pest especially when they are found to attack agricultural crops as they feed on plants eating the various parts from leaves to stem.And when feeding on weeds they are considered beneficial, although I would think, what is a pest or not really depends on which perspective we choose to look from. To the flea beetle, all it was doing was eating something available to survive.