In COUNTIFS, COUNTIF, SUMIF etc. the criteria need to be text strings so "greater than 2" will be ">2" but if the 2 is a cell value or the result of a formula then you need the & to "concatenate" that value to the operator, e.g. if you had today's date in Z2 that would be ">="&Z2 and it works the same if it's a function like TODAY()