You might have been like “Get me the heck outta Dodge!” You wanted or needed to get back to a stable OS, like Sierra (OS X 10.12) or El Capitan (OS X 10.11). Remember all the problems people had when they upgraded to OS X 10.13, also known as “High Sierra?” Oy, vey.
You may find that your current instance of OS X is too unstable for normal day-to-day usage or more heavy-duty tasks like development. We’re going to talk about installing a version of your Mac’s operating system (OS), known as “macOS” or “OS X,” on your Mac, older than the one you’re currently running, on a partition of your primary hard drive or on an external hard drive.
