The basic gun is the CZ 75B if you are looking at new ones. DA/SA, manual safety, no decocker so if you want to carry it hammer down then you need to manually lower the hammer to the half cock notch.
The CZ 75 BD is a decocker only model with no manual safety. My first few pistols were FNPs and Sigs so this is the setup I prefer, and what my first CZ75 was.
There are also the Omega models, which as already mentioned are convertible between manual safety and decocker and supposedly have worse triggers than either. Then again, people say the decocker models have bad triggers from the factory and IME they smooth out after a few hundred rounds of shooting/dry firing so take it for what it's worth.
There is the SP-01 which is basically a CZ 75B with a rail up front. The SP-01 Tactical is essentially a CZ 75BD with a rail up front and ambi decocker.
The Shadow 2 is more of a competition gun with a single slot rail in the front. The triggers are awesome.
All of the above use the full size CZ-75 magazines; the ones with the flat steel baseplate hold 16 rounds, the plastic baseplate ones hold 17, and the SP-01 comes with magazines that have a thicker baseplate and hold 19 rounds. OEM magazines are Mec-Gar, and the 16 rounders can be found for about $16-$17 each.
Then there are the compact models:
CZ75 compact: roughly the size of a Glock 19, steel frame, manual safety.
CZ 75D PCR: Similar to the compact, but with an aluminum frame, and decocker instead of a manual safety. Also the slide has a weird cut for the sights.
CZ P-01: This has a normal sight cut like the regular compact model, but has an aluminum frame with a rail in front, and like the PCR is decocker only. They have also made these with a steel frame in the past, and they have also made the P-06 in the past which was really just a P-01 in .40 S&W.
The compact models listed above come with 15 round magazines that will not work in the full size guns (because they are obviously to short). They can all use the full size magazines though. Pre-B magazines are different, and will not work in B models and vice-versa. Both are still available so if you get a pre-B make sure to get the right mags.
The polymer framed P-10, P-10C, P-07, and P-09 use entirely different magazines and really aren't CZ-75 series guns. Tactical Sport models like the TSO (Tactical Sport Orange) use another entirely different magazine that is wider and holds 20 rounds.
The CZ 97 B is a 45 ACP version that uses a Sig style locking block that locks into the ejection port, rather than the 1911 style lugs on the barrel that lock into recesses in the slide like on the CZ 75. I really wish they'd come out with a 10mm version; there are clones made in 10mm, but I want an actual CZ and not a clone.
Lastly, CZ is really bad about making really cool pistols and then discontinuing them all of a sudden. They did this with the stainless guns (which were available in matte or polished), .40 cal guns, Steel frame P-01, and a few others; so it is best to get what you want when it is available because if you wait a year you may be stuck having to source one through the used market.