If you no longer need a program on your computer, or if it is conflicting with other programs on your system, it's a good idea to uninstall it. Most of the time, the program's uninstaller will be adequate for this. You can find that by looking for the installer file, and then selecting "uninstall." This should remove all of the files associated with that program. There may be many other programs that wound up getting installed on your system that you're not even thinking about, and are just taking up space or resources.
Uninstalling a Mac application seems like an easy task -- just drag the icon from the Applications folder to the trash. This doesn't get rid of all of the files associated with that application, however. It might not always be necessary to get rid of all of an app's remnants, but if you're trying to reinstall an app that isn't working properly, you may need to take some extra steps first.
Angelo may have installed something that included them without him realizing it. Many freeware programs like WinAmp have partnerships that install bloatware and they aren’t easy to remove. Leo recommends the REVO Uninstaller. He shouldn't try to remove any scripts either, he could end up breaking something. He should also uninstall extensions. Angelo can also run the Microsoft Malicious Software Removal Tool (Start - Run - type MRT - Enter or Windows Key + R then type MRT and Enter).