The Four Path Model in its traditional form is the oldest of the Buddhist maps of enlightenment. It describes four progressive stages of awakening:

1. First Path, aka stream entry, sotapana in Pali
2. Second Path, aka once returner, sakadagami in Pali
3. Third Path, aka never returner, anagami in Pali
4. Fourth Path, aka Conquerer, Saint, Holy One, in Pali arahat, also spelled arhat or arahant

There are various ways to define these terms and use them.

For a discussion of how they tend to be used here on the DhO, it is highly recommended to look here: MCTB, more specifically here MCTB Models of the Stages of Enlightenment, and even more specifically MCTB The Theravada Four Path Model, as well as MCTB Was that Emptiness