Going to the loo
Cats tend to prefer the sort of litter used when they were kittens as they learn to associate the texture with going to the toilet.
As they are clean animals, they like their litter tray to be away from their food and water.
Cats are creatures of habit, so once they have a favourite toilet spot, they will continue to use it unless a lack of privacy, cleanliness or access causes them to look for somewhere else.
See also: Toileting