In PostgreSQL, the FLOOR() function is used to round a numeric value down to the nearest integer that is less than or equal to the original value. It effectively truncates the decimal part of the number, leaving only the integer part.

Example:

SELECT FLOOR(5.7); -- Returns 5 
SELECT FLOOR(-3.2); -- Returns -4 
SELECT FLOOR(10); -- Returns 10 (no change as it's already an integer)