Based on the powerful Box2D engine together with the easy to use features and powerful API of Farseer Physics Engine. See the full list of differences between Box2D and Farseer Physics Engine 3.0 here: DocumentationNote
This release does not support XNA 4.0. XNA 4.0 introduced some breaking changes that means you will have to change some files in order for the release to compile. The current version (FPE 3.1) in the source control does support XNA 4.0.