In doing so, the complete content of your disks is deleted. If you want to start over with a clean Mac, you have to reset the Mac factory settings and perform a clean installation. But you also include all the junk from previous installations. The big advantage is that you do not have to worry about it: you just have to press a button and have some patience. If you want to install this or all of the following updates, you can simply do so from the Mac App Store. High Sierra is the latest version of macOS (at time of writing).

Note: make sure that you always have a backup of all your files and data should something go wrong! You can do this, for example, via a Time Machine or another external hard drive. You make a fresh start on your Mac, without taking all the previous problems and it also comes in handy if you have taken over a Mac from someone else and want to start with a clean Mac. This can come in handy when you restore the Mac factory settings. If a new version of macOS becomes available, there are a lot of people who are considering a clean installation, a so-called clean install.

Boot disc for mac os sierra 10.12.4