Both of them. The first link returned by an internet search for "JAXP" is the Wikipedia article about JAXP. I encourage you to make use of available Internet resources which are extremely easy to find.
Think of the JAXP API as a wrapper API for SAX and DOM. Ideally, client code should be written to the JAXP interface rather than SAX or DOM directly. This way you can easily change your implementation without having to rewrite client code.