An aphorism is a maxim, a sentence or a saying that embodies a larger, final truth. It is lke trying to capture lots of truths about the world in one single sentence, like Friedrich Nietzsche claims in one of hi most famous aphorisms:

The aphorism in which I am the first master among germans are the forms of "eternity"; my ambition is to say in ten sentences what everyone else says in a book -- what everyone else does not say on a book.

There have been many famous writers of aphorisms throughout history so it is really difficult to tell which is "the" writer of aphorisms but I could give some good examples. For instance, Greek philosopher Epicure is famous for having written many aphorisms about the nature of pleasure in life. Another famous philosopher who wrote aphorisms was Nietzsche, who wrote a huge number of them in his book Beyond Good and Evil.