Perhaps you have come across this information already but if not here are the basics:
For the first time, rapes of men and statutory rape will be included in the official statistics that the FBI collects for the annual Uniform Crime Reports (UCR).
The FBI's change does not affect any criminal laws; it adjusts the definition only for statistical purposes, so that crimes under existing state laws will now be acknowledged, and counted by, the federal government.
Up to now, only the "carnal knowledge of a female forcibly and against her will" has been counted in UCR stats. In addition to counting crimes against men, the new definition will include rapes in which the attacker uses threats of violence, as well as all rapes in which the victim is a child and thus unable to consent.