IF
IF(A2 = "foo","A2 is foo")
IF(A2,"A2 was true","A2 was false")
IF(TRUE,4,5)
IF(logical_expression, value_if_true, value_if_false)
logical_expression - An expression or reference to a cell containing an expression that represents some logical value, i.e. TRUE or FALSE.
value_if_true - The value the function returns if logical_expression is TRUE.
value_if_false - [ OPTIONAL - blank by default ] - The value the function returns if logical_expression is FALSE.
Ensure that value_if_true and value_if_false are provided to the function in the correct order - this is the single most common source of problems with IF.
IFERROR: Returns the first argument if it is not an error value, otherwise returns the second argument if present, or a blank if the second argument is absent.
Specifies a logical test to be performed.