Now for some things to consider.
Since you are learning about handguns for the first time taking a NRA or accreditted local handgun class would be recommended. That way you not only get the basics,but you would be in a better position to know what you need rather than just want. Or both.
Local ranges, gun stores, or gun clubs should have these.
Defense and target shooting if the target shooting is competitive are two different things and demand, usually,two different shooting techniques. If it's for practice then one gun make will suffice.
Granted this all seems obvious, but am covering this again anyway.
Starting out shooting a pistol means that a .22lrf Ruger or Browning Buckmark are in order for example. These can do secondary duty as bullseye or for defense until the larger calibers are gone to. Not the best for defense, but will do in a pinch.
Cheaper to learn the basics with and ther's no flinch or recoil to worry about.
Glocks are user friendly. Light easy consistent trigger pull shot for shot. Manual of arms is simple. No levers except the slide release to worry about manipulating to fire or when the need to reholster.
Do recommend the 9mm. to start with if going with a centerfire caliber right off the bat. Cheaper to shoot ammo,less recoil, and a decent level of protection, this despite unwise "conventional wisdom to the contrary.
Nothing wrong with the larger calibers.Just making observations.
If learning then the Glock 17 or the Glock 34L is not a bad pick for starters. Want one for CCW later on? Then then the model 19 or 26. These are double action only trigger pistols.
If the 9mm. doesn't float your boat then go with the model 21 or SF21 in .45ACP.
Taurus makes a PT945 single stack DA/SA pistol.
Other pistol suggestions that will work.
CZ 75BD has a decocker, is traditional DA/SA triggered, and is a full size pistol that has an excellent track record.
CZ also makes the P01 for CCW or the RAMI.
Taurus makes the PT92, and it's sibling, the PT911 are full size or a step down from full size.
Ruger makes the P95 and the newer SR9.
Have experience with Ruger, Taurus, and CZ products. All will serve well.
There are a lot of good suggestions so far from the other members.
It might behoove you start a small reference library.
Gun Digest Book of Combat Handgunnery,written by Mas Ayoob is an excellent source of info. Easy to read, understand, and packed full of shooting techniques and all other pertinent info one needs. Comes out annually.
Gun Digest Books,Police Shelf, and Paladin Press are excellent sources for shooting information.
www.krause.com www.paladin-press.com www.ayoob.com
These are the sites for these books,DVDs, or videos.
The NRA has the NRA Firearms Source Book that is chock full of useful info.
Just things to consider.