In PostgreSQL, the CEIL() function, or CEILING() function, is used to round a numeric value up to the nearest integer that is greater than or equal to the original value. It effectively rounds up the number to the next higher integer. 

Example:

SELECT CEIL(5.2); -- Returns 6 
SELECT CEIL(-3.8); -- Returns -3 
SELECT CEIL(10); -- Returns 10 (no change as it's already an integer)