The System Management Controller manages many low-level functions on your Mac such as ambient lighting, battery and thermal management, keyboard backlight, and a host of others.
Why would you want to reset it? It was a common troubleshooting step you could try if you were experiencing an issue with your Mac. On my old MacBook Pro I had to reset it a couple of times and it fixed the problem (I just don’t remember what problem).
Reset M1 Mac SMC
Previously there were different steps to reset a Mac SMC depending on if it had a removable battery or not. You had to unplug the device, remove the battery, or press a certain combination of keys as it restarted.
But now? Apple’s support document says that if you have a Mac with Apple Silicon, resetting the SMC is as simple as restarting the computer. So ends one aspect of the DIY troubleshooting era.