Table UDFs are external user-defined C, C++, or Java table functions. Unlike scalar and aggregate UDFs, table UDFs produce row sets as output. A SQL query can consume the row sets as a table expression in the FROM clause of a SQL statement.
Scalar and aggregate UDFs can use either the v3 or v4 extfn API, but table UDFs can use only v4.
See User-Defined Functions for detailed information and examples.