I thought everyone knew why cats sharpening claws.
But it turned out, that it is needful to clarify this feature of our fuzzies.
The fact that a cat's claws always grow, as human)
But if we grind them with a nail file or cut with scissors, then cats grind off or as though tear off the top part of a claw about a surface. On the nature of the tree and the house about what is.
If they do not, then the claw, because it has a curved shape in the end just it will grow into a pad and cause unbearable pain.
That is why it is necessary to organize a favorite at least one place at home for grinding claws. The benefit of various scratching posts are almost any pet store.