"Snap Track" is just Atlas' trade name for their traditional sectional track. It will mate with almost any other code 80 track products from a variety of manufacturers. Atlas also manufacturers smaller profile code 55 track for the fine-scale purists; it should always be labeled as such in an advertisement.
I'd recommend sticking with the "old fashioned" code 80 if you are building your first layout. It's available anywhere, very reasonably priced, and practically indestructable. Others will argue that you should "do it right" and just start with the code 55 stuff and be done with it. To that I say that rarely does a modeler build just one layout in their lifetime; use what's proven and reliable to start with and down the road you can "upgrade" when you have a little more experience under your belt.
~BS
