When are they used:
SUM :- allows for the summation of a specific number of cells, both adjacent and non-adjacent.
=SUM(Start Range, End Range)
SUMIF :- allows for the summation of a range of cells that meet a specific criterion.
=SUMIF(Criterion Range, Criterion, Sum Range)
SUMIFS :- allows for the summation of a range of cells that meet a number of different criteria.
=SUMIFS(Sum Range, Criterion Range 1, Criterion 1, Criterion Range N, Criterion N)
