There are no standards established for the meaning of 12am and 12pm. It is often said that 12am Monday is midnight on Monday morning and 12pm is midday. This puts all the times beginning with 12 and ending with am in the same one-hour block, similarly with those ending with pm.
Answer: 12 O’clock in the afternoon is pm. Ante meridiem is generally referred to as AM, am, a.m., or A.M. Whereas PM, pm, p.m., or P.M. are typically abbreviated post meridiem.