I believe that's the remnants of a dewclaw. What would have been the fifth digit of the cats paw, but is on its way out because they have evolved to not need it.
I think they helped with swimming? But I don't know about that one
Actually that is called the carpal pad.
Cats have an extra forepaw pad called a carpal pad, found behind and above the large metacarpal pad used for walking. It is thought to provide an anti-skidding feature when cats land after a jump. Deep, fatty layers in the cat's footpads act as shock absorbers for jump-landings and other aerial acrobatic feats.
I think they helped with swimming? But I don't know about that one
Cats have an extra forepaw pad called a carpal pad, found behind and above the large metacarpal pad used for walking. It is thought to provide an anti-skidding feature when cats land after a jump. Deep, fatty layers in the cat's footpads act as shock absorbers for jump-landings and other aerial acrobatic feats.