When we create stems, we create individual tracks for different tracks within our mix.  I ask for stems from clients that started their song or piece in a program other than Pro Tools.  The ultimate goal while creating stems is to create a series of individual tracks that all start at the same point in time (so I can easily line them up within Pro Tools), and to break the song down into its individual tracks enough so that I can mix it.  When you create stems, the end result will be a folder of audio and/or MIDI files that you then send on over to me for import into Pro Tools.  Here are some general instructions on how to print stems, but you might want to look up more information about your specific DAW to ease the process.

How to Print Stems: