Drilling down allows you to see more information about the columns used within your search. If you own the pinboard you can drill down to the data beneath. Users you share the pinboard with can also drill down provide they also have access to the data on which the board was based.
To drill down:
Right click on the visualization or table cell of interest, and select Drill down.
Click on any of the listed data to recreate the search with that data included.