Drilling up
Drilling up means to replace the data you are drilling up on with the data for the parent element of that data. You drill up to compare data.
Drilling down
Drilling down means to replace the data you are drilling down on with the data for the child element of that data. You drill down to see more detail about data.
Example : Year contains Months, Months contains Weeks, Weeks contains Days, Days contains Hours, Hours contains Minutes.
Drill through or Drill by
Drill through takes him to a report that is relevant to the data being analyzed, also at the click of a mouse. For example, a tabular report that shows sales revenue by state can allow the user to click on it and reveal an analysis grid of the same data, or a heat map representing the data in visual form. It is called “drill through” because it is a feature that allows the user to pass from one report to another while still analyzing the same set of data.
Example: By Passing ID through a report block and getting a completely new report through open-document link.