TMPGEnc help

I am fairly new to TMPGEnc. I have a really stupid question...what is the difference between the stream types (ES and system)?

cheers

es splits the audio and video in two

ES stands for Elementary Stream(s):

When you choose ES, TMPGEnc separates the output file into Video and Audio. You can then merge (known as Multiplex or Mux) the two streams together at a later time - creating a whole, working video file.

System is the usual setting to choose because the output file is merged automatically, giving you a whole, working file.