SUMIF and SUMIFS are Excel functions used to sum values based on one or more conditions.
SUMIF: Adds values in a range that meet a single condition.
Syntax: `=SUMIF(range, criteria, [sum_range])`
Example: Sum sales in column B for all products in column A that are "Apple".
SUMIFS: Adds values based on multiple conditions.
Syntax: `=SUMIFS(sum_range, criteria_range1, criteria1, [criteria_range2, criteria2], ...)`
Example: Sum sales in column B for all "Apple" products in column A, sold in "Zone 1" from column C.
These functions are useful for conditional summing in data analysis.