Is dragging an application to the 'Trash' uninstalling it?

Yes for the most part it is. It will leave files in your library though which take up little room and won't affect your Mac. One highly recommended application is AppZapper which will remove everything (with a cool zapping sound)...

 

AppCleaner does the same thing and it's free.

 

Indeed a simple delete sufficies, but if you want to be exhaustive..

Deleting the application normally will delete the application. But there are exceptions.

If you think, or have a hunch, that the application runs in the back-ground, you may have to do a more complete uninstall. Normally the readme on the installer that came with the application will guide you thru this.

Have a peek at your account preferences, login items tab. This may give some useful indications on whether the applications is stand-alone or not.

Sometimes apps have a preference pane. You would, in all logic, want to delete this also. Select delete normally suffices in preferences pane.

If your application in web centric, you may wish to look at the keychain application to remove any information there that relates to your application or the web account it uses.

Also, don't forget the preferences file in [library/preferences].

Some application suites (like Adobe) have shared services. Delete the shared service only if no other applications of the suite remain.