The Brief: Age play is a kink that involves someone roleplaying as someone younger.

Bluesquiggle
DEEP DIVE

Ageplay is an umbrella term for kink relationships that involve at least one person roleplaying as a younger age than they actually are, usually as a baby, toddler, or child. Age play relationships can be platonic and SFW or they can be more overtly sexual and involve BDSM dynamics, as is the case for DDLG.

There is debate about the exact definitions of these terms, which can vary from person to person.