With BigSur, Apple has updated the widgets to be more visually compelling as well as useful. Widgets are helpful especially with compact organization so that you can digest data in a quick glance. They're in the Notification Center, and like iOS, you can tweak, remove, add, move, and resize each widget.
How to edit widgets
Open the Notification Center (Click the date and time on the upper righthand corner)
Scroll all the way down and click "Edit Widgets"
On the left, select different apps you'd like a widget from
Then in the middle column, select the type of widget you'd like the app to show
Click the green plus sign (+) to add a widget
To remove widgets, click the minus (-) button to remove
When finished, click "Done"
You can also customize the size of widgets by selecting one of the three sizes: S, M, L (small, medium, large).