argumentlist = any combination of numbers, cells, or ranges
AVG returns the average (arithmetic mean) of its
arguments. Blank cells and strings are ignored. The
function is given by:
AVG(A1, B9, J32, F16) = 21.125, where A1 = 12, B9 = 34.5, J32 = 22, F16 = 16
AVG(A1, A12..H13, 111+32) = 135.67, where we don't really care what is at those variables, but which shows that you can use numbers, ranges, and expressions all together as arguments for AVG.
Excel function: AVERAGE