This command is not only for look libraries into our system it could be use to find files too.
I personally used it because I need to check if the was a library installed on my machine to fix a library dependencies problem
locate libstdc++.so.6
The result of exec this command should be something like this:
So thanks locate I found that the library I need was on my machine but in a different path and that fixed my problem.
Update: Related post
If you wanna know all your application library dependencies you should have a look to this post