2020 Worksheet allows you to open and work with multiple files at the same time. Each open worksheet file is displayed as a tab which allows you to easily switch between them. For Example, in the following image I have 3 worksheet files open, A, B, and C.
Lets say I have a need to see both the A and the B Worksheet at the same time. If you right click on the tab of a worksheet file you will have an option to create either a new horizontal or vertical tab group. This will split the screen and display that worksheet file in a new group, allowing you see both of them at the same time.
In this example I have right clicked on the B Worksheet tab, and chosen "New Vertical Tab Group". This will create a split screen effect putting the B worksheet into the new group. I now have the option to see A or C at the same time as B.
If I wish to close the new group, and move the B Worksheet back into the group containing A and C, I can right click on the B tab and then choose "Move to Previous Tab Group"