I think I am having trouble understanding this function.
vlookup stands for vertical lookup where you search 1st argument in 1st column of 2nd argument (usually a range). the 3rd argument sets the output and stands for column number you wish to return. the final, 4th argument affects if you want to return exact matches 0 or close/partial matches 1 (especially useful when used on numbers where you need to target a "between" range)