It's amazing when people say that dragging apps into the OS X's Trash folder uninstalls them, because it's not always true. When uninstalling Google Chrome by dragging the app to the Trash, for example, all the browsing history, bookmarks, and so on can remain on the Mac.
Simply throwing an application in the trash won't get rid of everything associated with it. Those additional files are your personal settings and preferences, and they are excluded from the application package file so each user account can have their own settings, and to make it easier to flush if something gets corrupted.
These sorts of files are put in your /Library/Application Support and /Library/Caches folders. In OS X, we'd suggest simply deleting apps by dragging them to the Trash and then, if you want, deleting personal files associated with them from your own Library folders as an extra step.
Unlike with Windows computers, a dedicated uninstall app probably isn't necessary. (The reason uninstallers are so essential for our PC-using brethren is that library files can be dumped in the Windows folder and only a cryptic reference in the registry tells you where to find them.)
There are, of course, a few badly behaved Mac applications out there, but these are definitely outliers. If you have an app you just can't get rid of, it might be worth using something like AppCleaner, but in general it's unnecessary. Admittedly, AppCleaner is donationware, so you don't have to pay for it, but the office copy sits quite unused so far...