OK so sometimes cats scratches tree in order to keep their claws sharp so is it true that every time a cat or any other feline uses it claw, there claws become less sharper
A cat claw will get less sharp over time and this is why cats sharpen their claws,a cats claw is layered like an onion so when a cat sharpen its claw the outer layer falls off exposing a fresh sharp claw.
If you take a look at your cats scratching post you will probably find the outer shell of your cats claws,a cat has two ways of sharpening their claws one is by scratching and the other is by using its teeth to remove the outer layer of the claw.
Most cats have retractable claws on the front legs,The claws on the hind legs can not be retracted fully but they still stay fairly sharp but nothing compared to the claws on the front legs.
By retracting the claws on the front legs they stay protected against wear when the cat walks,when a cat catches larger prey animals the cat uses the powefull hind legs and claws to tear the preys belly open cats do the same when they fight each other.