A poster child (sometimes poster boy or poster girl) is, according to the original meaning of the term, a child who had some disease or deformity whose picture is used on posters or other media as part of a campaign to raise money or enlist volunteers for a cause or organization. Such campaigns may be part of an annual effort or event, and may include the name and age of a specific child along with other personally identifiable attributes.
"Poster child" has become a metaphor for a person of any age whose attributes or behavior are emblematic of a known cause, movement, circumstance or ideal. The person in question is thought of as an embodiment or archetype. This signifies that the subject's identity is synonymous with or at least representative of the associated ideal in its most favorable or least favorable aspects.