The macOS Sierra has built in functionality that helps you clean up and free up space on your Mac. The Optimized Storage allows you to move files that are rarely used, photos, iTunes movies that you've seen into the cloud. The file link are kept in the same place, and when you decide to access them they are downloaded back to your Mac. In addition you have the option to clear your trash (older then 30 days)and cache files, delete downloads that have been opened, etc. In short, Optimized Storage gives you a set of automated tools to cleanup your Mac and free up storage.