Here is Wikipedia's definition of a false flag:
False flag (or black flag) describes covert military or paramilitary operations designed to deceive in such a way that the operations appear as though they are being carried out by entities, groups or nations other than those who actually planned and executed them. Operations carried out during peace-time by civilian organizations, as well as covert government agencies, may by extension be called false flag operations if they seek to hide the real organization behind an operation. Geraint Hughes uses the term to refer to those acts carried out by "military or security force personnel, which are then blamed on terrorists."
Here is a list of various false flags from the Washington Blog that are admitted to have occured. (Note that at least one seems not admitted but possible.) The list is well worth your time.
Trust no government official.