Elementary stream (ES) contains only one type of encoder output data like video or audio.
A process generating an elementary stream into packets is determined as a packetized elementary stream (PES). It is made for forwarding ES. Each packet has a header. It consists of different information like timestamps, packet priority, and other information. It means that the elementary stream format will be contained in the header data. Then PESs are encased into the program stream (PS) and transport stream (TS).