This is one of my favourite shortcuts. It's a great way to find out what's going on in a sheet you didn't build or if you're still learning tableau, It's a great way to direct a workbook.
Tableau Notes: https://j.mp/3gbaPgw
When you want to see details about all of the elements in use in a viz, select the Worksheet menu, and then click Describe Sheet. For details about a field (such as data role, data type, domain, aggregation, calculation formula), click Describe in a field's context menu in the Data pane. You can then share those details with someone else by copying that summary text.
One of my favourite small features in Tableau: Describe sheets and fields: Quick tip