Here you go: “A marathon or half marathon pacer is a volunteer runner that runs a race at a specific pace for a target finish time. Pacers are usually veteran runners that have racing and pacing strategies they have mastered which they utilize during the course of the race. Pacers wear some type of signage/object such as a sign, balloon, or shirt identifying their target finish time.”
Link: https://halfmarathonforbeginners.com/what-is-a-pacer-in-runn...