All software in Mac OS X is installed in /Applications, which can be found in the Finder sidebar
The most Mac applications don't have to be installed, you just have to copy the applications in the Applications folder. Normally, all installed applications that are in the /Applications folder appear automatically in the Launchpad.
You can uninstall applications that don't come from the Mac AppStore simply by moving them in the Trash, applications from the Mac AppStore can be uninstall by entering Launchpad, holding the option key and clicking the little x that appears at the app-icon.
The location of the applications folder in the Finder: