Worksheet in the Tableau screen is the area where you create the views for data analysis. By default, Tableau provides three blank worksheets when you have established a connection to data source. You can go on adding multiple worksheets to look at different data views in the same screen, one after another.
You can add a worksheet in two ways. Right-click on the name of the current worksheet and choose the option New Worksheet from the pop-up menu. You can also click on the small icon to the right of the last sheet name to add a worksheet.
Staying in one worksheet, you can have a quick preview of another worksheet by hovering the mouse on the name of the other worksheet.