What are single row and multiple row functions?

Single row functions operate on a single row to return a single value per row as the output. They can accept one or more arguments but return only one result per row. They are also known as Scalar Functions.

Multiple row functions operate on a group of rows or a set of values and return a single value calculated from all the values present in a column instead of providing the listing of all of the rows. They are also known as aggregate functions.