When you run the program, you'll see a list of all the units connected to your Mac. Once you select the hard drive you want to analyze, you'll see a list of all its different folders organized by increasing size.
This way, you can find out which folders take up the most space on your memory. OmniDiskSweeper lets you not only control the storage space, but also copy files onto other hard drives or delete them if you don't need them anymore. Be careful when deleting files, though, since the program won't let you recover them if you delete one by mistake.
In short, if your hard drive is too full and you need to locate the largest files, this simple program will help you do so in an efficient way.