Hi Mah, 'Get out' means to leave a place or exit something. For example: "Please get out of my house now!" 'Get off' means to remove yourself, someone or something from on top of something else. For example: "Please get off my car!" (A person is on top of the person's car and is asked to come off) Hope this helped :)

Just to add to Albert's answer... You might remember we use "on" for public transport such as buses, trains and planes (on a plane, on a bus), even though we are not physically "on top of" the vehicle. So you would use "get off" if you were a passenger on a train, but you would use "get out" if you were inside a car or taxi.