Let's start with a simple Function that can be really useful - LARGE.
The Large function searches through a range of cells and returns the largest value or the 2nd largest or 3rd largest..... whatever you specify.
In this example, Excel goes through the range in B4 through B11 and returns the highest value which is 800. If the formula had read =LARGE(B4:B11,2) then the resulting answer would be 500 as that is the 2nd highest number. Quick way to retrieve something.
And of course, Microsoft thinks of everything so the function SMALL does the exact opposite.