In the wild, cats have the desire to relive themselves on sand or sandy soil in order for them to easily bury their waste.
So when cats became domesticated, some genius invented the litter box in order to simulate that sand or sandy soil that cats desire.
Modern Litter box fills are usually loose granular material that is absorbent and most importantly, odorless.
The most common material used is clay, but in more recent times, there are already much safer, and easier to clean materials available such as silicon granules.
People are often times very protective of their pets and are generally prone to always keep them inside the house.
In response to this, cat litter design is improved such that litter nowadays are spill free and would absorb the smell from cat waste.
There are even some designs that are covered in order to give the cat seemingly needed privacy.
Some expensive cat litters today even have automated cleaning features which of course makes it more convenient for the cat owner.
A much more complicated, but much more convenient way of getting rid of cat waste is o toilet train you cat.
In Japan, several animal behavior researchers have found a way to train a cat to use the toilet, but this takes much more time to do because of the fact that you need to train you cat while it is still a kitten.
Always remember, when getting a litter box for your cat; always keep it litter deep enough for the cat to dig.
Also place the litter box in a quiet place so that the cat will not be interrupted while doing its thing.