It's hard to describe, simply as I've never played a strategy game like it. It's got the usual 'take unit, click on unit, have unit attack other unit' mechanic, but it does it with real-world equipment, and there's a lot of other aspects beyond "shoot the mens" you need to take care of. Everybody's going to need to be resupplied at some point, which means you'll need to run logistics trucks out to their position, or else drive/walk them back to a FOB. You need dedicated recon or else you'll walk your expensive Abrams or T-80s into an ambush, because they can't see nearly as far or nearly as well.
Then there's the deck system, or how you create your force...
I dunno. It's tough to describe. Plenty of good YouTube videos showing gameplay out there, though.