What is Drill Through Report in SSRS ?

Drill Through Reports : Drill through reports is when user click on the values ,redirect the user to another detail  report. Drillthrough reports commonly contain details about an item that is contained in the original summary report .These are standard reports that are accessed through a hyperlink on a textbox in the original report.
 You can make a drill through report by right click on the textbox that you want to be hyperlinked.