This formula in particular allows you to take a partial list with some blank data and compare it to a master list and retrieve the blank data. For example, let's say we have a list of 10 student names that we need Student ID's for, and the only point of reference that we have is a master list of all 200 students and their respective ID's. The formula allows us to match the name from our list to the master list, and bring a copy of the student ID to our list. Attached is a spreadsheet outlining these details in a more visual method.
Formula for data comparison in Excel
B - information trying to find (A student ID for example)
D2 - column to compare from (Our list)
A2 - Column to compare to (the master list)
As mentioned, your output will be the student ID's for all the students in our list.