In lea-mans terms what are tubulars, clinchers, and what is a standard wheel tire called?

I have a 2009 TCR advanced (105 components) with mavic cxp 22 and Michelin pro 3 tires

I have the opportunity to pick up locally a very lightly used Pair of Zipp 404's Tubular wheels, ZIPP skewers, Zipp carbon brake pads and 10 speed cassette, for $600.

How much of an upgrade would it be for me. I ride daily and like to go as fast as i can, and weekly club rides. I'm 45 185lb

Clinchers are where the tire is open on the inside, a tube goes inside it, and it clings to a kind of hook on the rim on each side. Tubulars are fully enclosed with the tube already inside, and are glued to a rim that has no hook.

Zipp 404 would be a huge upgrade, although I would personally not run carbon tubulars for daily riding. They would be racing only for, but there are those with different opinions. Tubulars are a little trickier to fix flats mid-ride, although they seem to flat less... and you can continue to ride (gently) on a flat tubular tire if you had to.

Yeah, the ZIPP 404's wouldn't be a wise training wheel- hit a deep pothole and the carbon might go- but great for racing.

how much of a gain do you think i would get?
I have done a lot of searches in here but being a noob i'm not sure what im comapring to, most of the post seem to be talking about tubulars vs. clinchers ect. not comaparing the type of wheel's I have to a tubular clincher....

layman.

Only a wind tunnel test can give you a specific number, but the faster you go, the more important aerodynamics becomes. Honestly, most equipment gives you a tiny improvement compared to what you can do by just training properly. If you're getting these wheels because you want to add 2 mph to your average speed, forget it. If you're losing races by a fraction of a second, it's worth a shot. If you just want to get a good deal on some hot looking wheels, that's up to you.