COUNT is for adding up a range or ranges of cells that contain a number stored as a value.
COUNTA is for counting the number of filled cells in a range.
COUNTBLANK is for counting the number of empty cells in a range.
COUNTIF is for counting the number of cells in an individual range that meet a given criteria.
COUNTIFS is for counting the number of cells in multiple ranges that meet a given criteria.
FIND is for finding the starting position of a text string (case sensitive) within another text string.
IF is for performing a logical test and returning a TRUE or FALSE value.
IFERROR is for evaluating a formula or cell reference and returning the formula value if no error, else, if an error, returns a value from a different formula or cell reference.
LEFT is for extracting a number of characters from the left most side of a text string.
LEN is for counting the number of characters in a text string.
MID is for extracting text from part of a text string.
RIGHT is for extracting a number of characters from the right most side of a text string.
SEARCH is for finding the starting position of a text string (not case sensitive) within another text string.
SUM is for adding numbers together from and individual cell, single or multiple ranges.
SUMIF is for adding numbers together from an individual range of cells when one matching criterion is found.
SUMIFS is for adding numbers together from multiple ranges of cells for multiple matches.
VLOOKUP is for retrieving data from a column and on a row where an exact or closest match is found in the left most column of a range of cells.