Transformers is a line of toys designed and produced by the company Takara (well, originally produced in some Japanese toylines called Diaclone and Microman), and then they were produced by Hasbro, too, for the American market. They are not only an action figure of robots of the animated series, but they can be "transformed" into a car, an animal or a particular device (for example, a mobile phone, a radio, a gamepad, and so on). Transformers can be good (Autobots), guided by Optimus Prime, or evil (Decepticons), guided by Megatron.
These names I used are from the European and American market...if they are different, please, let me know!