Now when you run First Aid, Disk Utility will verify the selected drive and if it finds an error, automatically try to fix the problem. The main change is that First Aid no longer has the ability to verify the drive independently of repair. With the advent of OS X El Capitan, Apple made a few changes to how the First Aid feature works in Disk Utility. Disk Utility's First Aid feature can verify the status of the hard drive and, if necessary, perform a repair of the hard drive's data structure to prevent minor problems from becoming a big problem.
