What are command scopes and what are they used for?.

What are command scopes and what are they used for?.
When editing the command bar for model-driven apps you have different scopes that determine when it renders.
This article will give some extensive information on the different commanding scopes:
https://learn.microsoft.com/en-us/power-apps/maker/model-driven-apps/commanding-scopes
Cheers,
Sancho