Great question. The honest answer is that we’re not entirely sure – but, there are some theories! Although they look a bit like wrinkles, they’re formed in a completely different way, so some scientists think that they might serve a specific purpose. Given that you only find them on your fingers and toes, one theories is that they help us to sense things via touch. Some research has shown that very tiny vibrations that are produced by fingers moving across a surface means that you are much more sensitive to the texture of that surface, than if your fingers were completely smooth.
However, that doesn’t explain why everyone’s fingerprints are unique, and we’re not sure at the moment why that’s the case!