Hi Sue,
I can tell you what I think, and that is that the 16th lancashire fusiliers, or 2nd salford pals, weren't regular soldiers. Pals battalions were called that because they were made up of friends, workmates, social clubs etc, then obviously given military status.
Thats my view on it, but I think ManMack is the person to explain it better!
Out of interest, what was your great uncles name? and how much do you know about his time in the war? I highly recommend reading the salford pals by michael steadman. I learnt alot from it, and I'm now able to start creating a memorial page to my great grandfather.
Good luck, Regards, Benn.