I think that it is the letter and column of the cell. For example the first cell's cell reference would be the letter "A" and "1" = Cell Reference A1.
This is pretty handy to know because when you enter formulas such as
sum=(A1,A2,A3,A4) then it become pretty darn difficult.
If I'm wrong then slap me!
(But I'll imprisonment you!)
Wah
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Greetings mortals, my name is Wah, Arch Lich Wah.