Check out this video, important info related to Cisco Switches is at 13:07 called the Superloop
https://www.youtube.com/watch?v=3rZWyZxnG80
come on. That has to be the worst link to a video to try and explain anything. skip to 13:07? really? Please. It’s bad. don’t link that. There might be something good in there that is attracting your attention, but wow. No clicky advised.