Appriority is an application that can help you optimize your Mac. The application can make your Mac work faster by automatically suspending applications that are on the background. As you may know, apps that are on the background or inactive still use CPU power. When you are running multiple applications on the background, these can slow down your Mac by not letting applications on the foreground. One great thing about this app is that you can customize the applications that will be suspended. You wouldn't want important applications to be suspended just because they are on the background. One example of this are file servers, FTP servers, remote assistance apps, etc.
When you first launch Appriority, a window will explain in detail what the application does and how to set it up. Then the application's main window will show all the running applications and the CPU% they are taking. From the preferences window, you can add apps to the list of apps to be suspended when they are inactive.
In short, if you are a user who needs to run very CPU intensive apps and the apps that are on the background get on the way, Appriority can help you. I like the idea that you can tell it what apps to suspend and you can resume them with a hotkey.