Safe mode prevents your Mac from loading certain software as it starts up, including login items, system extensions not required by macOS, and fonts not installed by macOS. It also does a basic check of your startup disk, similar to using First Aid in Disk Utility. And it deletes some system caches, including font caches and the kernel cache, which are automatically created again as needed.

Safe mode is particularly useful when you’re trying to resolve an issue that doesn’t seem to be associated with using any particular app. As always, keeping your software up to date is the first step toward resolving any software issue.