Reset NVRAM/PRAM & SMC on Mac computers

Quick Links and how to for resetting NVRAM/PRAM and SMC

How to reset NVRAM or PRAM on your Mac
https://support.apple.com/en-us/ht204063

Power on, quickly hold Option + Command + P + R, wait for startup sound, release.

How to reset the System Management Controller (SMC) on your Mac
https://support.apple.com/en-us/HT201295
for Mac Notebooks:

Shift + Control + Option then Power button, hold 10 sec. then release, Power back on.