The document summarizes changes brought by the America Invents Act to U.S. patent law and practice. Some key changes include transitioning from a first-to-invent system to a first-inventor-to-file system, expanding the definition of prior art, creating new post-grant review proceedings like post-grant review and inter partes review, expanding prior user rights, and changing treatment of errors in inventorship. The changes aim to harmonize the U.S. system with other countries and improve patent quality and challenge procedures.