Your Mac’s parameter random-access memory (PRAM) stores important information such as the type and identity of your OS X system drive, the presence of any other internal drives, the number and type of connected devices, screen resolution, and speaker volume. If your Mac isn’t acting as expected, a PRAM reset is usually the first and easiest troubleshooting step to try. You’ll also want to make sure you preform a PRAM reset after you replace your Mac’s hard drive, unless you like waiting five minutes for the system to boot while it searches in vain for the old missing disk.
So basically, it stores configuration information about hardware, both internal & external.
By resetting the PRAM, we're changing all its hardware settings -- incl. what it might "remember" about external devices -- back to fresh. We're literally wiping its memory of its hardware experiences.
Note, this will *not* affect any other external devices -- just your computer itself.
If you have an external monitor connected, you might need to unplug that before the PRAM reset (again, unplug any & all devices from the macbook before doing this).
After the PRAM is reset, then settings like volume, brightness, screen resolution, and its "memory" of external hardware devices... will all be clean/fresh.
While I'm reasonably confident this shouldn't *harm* anything, I also cannot make any guarantees. You do so at your own risk.
JustAnswer is an information site, and I am operating as an independent contractor to provide you with information.
I wish I could give you a better response!
But here is the Apple support article about resetting PRAM (also known as NVRAM), and what Apple has to say about it: