A maxim is a brief statement that contains a little piece of wisdom or a general rule of behavior. Maxims are sometimes written by a single author, for example in the form of philosophical quotations. When a maxim has no specific author, it becomes a kind of proverb – something that just emerges from the culture and survives because people use it, not because any specific person wrote it in a book.
The defining characteristic of a maxim is that it’s pithy – that is, it packs a lot of meaning into just a few words.
Maxims are very nearly the same as aphorisms. The only difference is that maxims are often more straightforward. Whereas aphorisms tend to use metaphor, maxims may or may not do this.