What is difrence between am and pm?

AM and PM are abbreviations used to denote time in a 12-hour clock format. AM stands for "Ante Meridiem," meaning "before noon," covering the hours from midnight (12:00 AM) to just before noon (11:59 AM). PM stands for "Post Meridiem," meaning "after noon," covering the hours from noon (12:00 PM) to just before midnight (11:59 PM). Essentially, AM indicates morning hours, while PM indicates afternoon and evening hours.