what is the difference between clincher wheels tubular, tubeless.

I run into different names for all these and still can't figure it out. any help would be great.

Clincher is when the rim has an U-shape profile, open to the outside. The tire is also an U-shape, and is mounted with the tips of its U nestling inside the tips of the rim U. In the cavity thus formed you stick a tube. Tubeless is a version of clincher, where the rim and tube is designed and prepped in a way that give an airtight seal w/o having to use a tube.
Tubular basically is tire and tube combined into one. The are glued on to rims with just a rather shallow concave surface instead ov an open U-shaped profile.

Clincher is the "normal" style where you have a tube and a tire that you snap on over the raised sidewalls of the rim. Tubular is a full wrap tire and fabric carcase that is sewn along the inside seam. These are used on special rims with no sidewall flanges. They are actually glued to the rim during mounting them. If that sounds like a lot of bother for anything but specialized use you're right, they are. Velodrome racers and some road racers typically use them for the light weight and good performance they offer in exchange for all the fussing. Tubeless is fairly new. It involves sealing the spoke nipple holes so the rim will hold air and using special tires with a more aggresive holding bead to air up the tire without the need for a tube. Again you're only going to find this on some special bikes used in competition or by some riders that want to copy the racers. Typically these tubeless setups are found on mountain bikes used for cross country racing.

so from reading the two awsome posts. I would say that I should be looking for clinchers. since I have a 2010 trek 1.2?

Yes. Your bike came with clincher tires- Bontrager Race AW, size 700x23c specifically. You can substitute slightly fatter tires if you like: 700 x 25C or 700 x 28C maybe. Any "700C" tire will fit the rim- whether the tire clears the frame is the limiting factor.

thanks. from what I have read is 25 is the largest that will fit and them some actually won't even though they are 25. but right now I'm riding bontrager select B tires. would like to upgrade just a tad