RTSP: Real-time streaming protocol
Real-time streaming protocol (RTSP) is a network protocol that controls how the streaming of a media should occur between a server and a client. Basically, RTSP is the protocol that describes what happens when you click "Pause"/"Play" when streaming a video. If your computer were a remote control and the streaming server a television, RTSP would describe how the instruction of the remote control affects the TV.