Packed bitstream

Using Avidemux, and when I drag some movies in…i’ll get a prompt something like…this has a packed bit stream, would you like to unpack it?
I never do and wonder, what is suffering from my video or audio? What does this do? Thank you

This might help.

Welp, i’m having NO luck with avidemux. I’m not to dumb, but it is hard for me to use, plus i just don’t understand this whole conversion process…
unpacking bitstream, saving, converting to different audio, video, blah blah blah.
Please, is there a SIMPLE program to unpack this stream and also CHECK the dvds prior to burning, to see if they’re ok?