How can I uninstall a problem app on my Mac?

How I can uninstall something that won’t just go away when I delete it, but also doesn’t have a built-in uninstaller; I downloaded and installed an application on my Mac and now I’m having trouble uninstalling it. What can I do?

How do I hide folders on my Mac?

I have some files on my computer which are rather confidential and I’d like to hide them so other users won’t see them. How do I do this? P.S. I’m on a Mac