Common Excel Functions: Instructions with picture references

Enjoy these detailed instructions of 13 functions in Microsoft Excel that no one should be without. These instructions are accompanied by descriptive screen shots. Intended to be reference material for beginners and intermediate users.
Make Excel work harder for you so that you can become a greater asset to yourself and to your employer. Some of these functions will leave you accidentally impressive to many of your peers. So let's get started!

Functions Covered:
Average
Count
CountA
Countif
Countifs
If
Max
Median
Min
Sum
Sumif
Sumifs
Vlookup