A somewhat formal or literary term referring to people of later times, often used in historical or philosophical contexts.
They left a record of lessons that should be passed on to future generations.
This inscription was carved for posterity.
後人 refers to people of later generations, the direct opposite of 先人, who came before.
Compound of 後 (after, later) and 人 (person, people). The exact historical derivation is uncertain, but the spelling is conventionally associated with the meaning 'people of later times'.