A vlookup is a spreadsheet function which looks for a specified value down the leftmost column of a table and when it finds that value, it returns a value from the same row.
We need to tell it what to search for (a red star in the below illustration), where to search for it (in the Shapes table in the below illustration) and which column number to return the value from (column 4 in the below illustration). The result of this request would return the red minus sign.
An Example from the Real World
You know how to use a dictionary right?
You have a word and you go looking in a book for that word and you get its meaning. That’s what a vlookup is. Using the vlookup function, you can get excel to search for a word (or number or string) in a list and return a value from the same line.
… and in order to do so, you’d need to tell it what to look up (the word “elucidate”), where to look it up from (the table), and which column to get the meaning from (in this case, column C which is the 3rd column along in the table)