How to reset PRAM on Intel Mac laptops

Overview

PRAM (also called NVRAM) is a small amount of memory that your Mac uses to store and quickly access certain system settings. Resetting the PRAM can resolve some issues with sound settings, display resolution, startup-disk selection, and time zone. These steps only apply to Intel-based Macs. 

Instructions

1. Shut down your machine. 
2. Press the power button and then immediately press command-option-P-R.
3. Hold down keys for about 20 seconds:
   1. On Macs that play a startup sound, release the keys after the seond chime
   2. On Macs with the T2 Security chip, release the keys after the Apple logo appears and disappears for the second time
4. Let go of the keys and let your Mac reboot normally.