Explainshell.com
Awesome website that explains shell commands.
Example:
https://www.explainshell.com/explain?cmd=cat+urls.txt+%7C+xargs+-n+1+curl+-O+-L#
From the front page you can enter a command and it will explain what each part of the command does.
Do note it has limits and do not know commands like jq etc.
Bonus! it supports both dark and light themes.