Water Heater

Hi I have a 1999 Pontiac Grand Am Gt well I been told my Pep Boys a few weeks ago to a couple of months ago anyways that my intake system is going out well here in the past few days my car will not hold water, antifreeze, as soon as putting water in the reservoir it immediately leaks right on to where put 4 jugs of water before it finally quits coming out. Then while on the road driving the water gushes all out. My friend was a distance away to see if the water is leaking and as I'm driving water is gushing all out. It's over heating. It won't hold anything at all. I called pep boys early this morning to let them know that my car has got worse now and they said to me which they have never lied to me, been trustworthy and waived fees for me as well. My friend works up there so he makes sure nobody takes advantage of me and gets the work done. Anyways he said that my intake system is now shot and my water gasket as well, he explained to me about it but can't explain it as good as he did anyways that I need to bring it in immediately to get it fixed and it's not driveable at all right now. My engine is burning, smoke and stinks real bad. So the total cost including labor is $650.000. My question is what is a water gasket?