You have several good answers here, but I'm going to throw in my 2 cents too.
For one, Touchwiz. From this thread I am assuming that Touchwiz is the Apps screens or "grid" after the home screen?
The home screen
is the launcher. The grid with the apps in it is the apps drawer, unless I misunderstand you.
Also, from this conversation it seems you guys are referring to this as a "launcher"? Makes sense.. I mean it is launching the apps after all right? But I assumed that this was part of the overall "theme" of "layout" of this particular OS. I had no idea that this could be customized.
The launcher is your home screen, so it can show much more than various apps you can launch. There are hundreds of different widgets you can put on it, and most launchers can have multiple screens to scroll through, so you can put full screen widgets on different screens. Lots of the widgets are scrollable, so you could put maybe a twitter widget (there are a ton of sources for different twitter widgets) and scroll up and down or side to side through the tweets. My favorite widget apps at the moment are Android Pro Widgets, Beautiful Widgets, Elixir 2, and Fancy Widgets. Plus, lots of apps have their own widgets that perform different functions. For instance, 1Tap Cleaner has a widget that will clear your app caches when you tap it, Beautiful Widgets will show the current time, weather, forecast, and battery level in it's widget. They all do different things. Just know that they use up resources. When you have a choice between a widget and a shortcut that will perform the same action, pick the shortcut.
So.. if I am understanding you guys correctly, I could download an app like the ones you guys were talking about (ADW and LauncherPro) to replace this functionality in my phone?
Now let's say that I did that. Once I install the "launcher", will it automatically take over for the stock launcher or "touchwiz"? Or will I have to do something or delete "touchwiz" all together so that I do not have multiple launchers trying to work at once?
You can download any one you wish. I actually maintain a list of them in
The Big List of Home Launchers. Most are similar to your stock launcher (TwLauncher). The big plus in using a launcher that looks similar to stock is that particular launcher's options and widgets. The main launchers you hear people use most are ADW.Launcher, LauncherPro, and GO Launcher EX. They're mostly like stock, but have tons of inherent options and downloadable themes. Some of the free ones that are really different are Claystone Launcher, Hi Launcher, NetFront Life Screen, and Rocket Launcher. Read through the market descriptions, look at the screen shots, and try as many as you wish. You don't have to uninstall anything to try another. In fact, I usually have 3 or 4 on my phone at any given time, and pick the launcher I wish to use with Home Chooser Flow. But I'm a big fan of trying out new stuff all the time.
BTW, my personal all-time favorite is SPB Shell 3D, but I only run it when I want to show off a phone. It's very heavy on resources and is a major battery drain, but the wide view which rotates is freaking
awesome.