Landscaping your pubes means trimming/shaving your pubes instead of letting them just grow into a wild bush.
Some guys shave them all off. Others just trim them back. Others also shave the hair off their balls. It just depends on what you and your significant other (if applicable) prefer. It can be a cosmetic decision.
Some do it so their sex partner's don't end up with loose strands of your pubic hair in their mouths while orally pleasuring you.