From the webstie
"Maintaining a Mac is a lot easier than a PC but it still requires some work. After a few years of use, your hard drive space starts to shrink and finding the right files to delete isn’t always obvious.
"MacPaw is releasing a new app to help people free up more space on their Macs. It’s called CleanMyMac 2 and it will dive deep into your harddrive to clean out all the crap you don’t need.
"CleanMyMac 2 helps you find more space for the things you love, so you don’t have to put your new photos or videos on an external harddrive. Once you install the app, it scans your harddrive and a few seconds later it will give you a summary of everything you can toss in the trash. We took it for a test run last night and found it very easy to use, and it had a nice interface.
"Unlike some other apps, it will also tell you which system files you can throw away, like caches, logs, archives, and a bevy of other options. However, Apple wouldn’t approve it for the Mac App Store because Cupertino doesn’t like that it cleans up system files that most apps never touch. MacPaw says it’s totally safe, and they have a good reputation, so I wouldn’t worry too much about it."