A lollipop in F1 is a large sign mounted on a long pole held by a pit crew. The lollipop was used in older F1 races to signal a driver about his pit box location, when to change gears, and when to exit the pit box.
The sign typically has a handle on the back, which the crew member holds, and a circular disc on the front with the team’s colors and logo on it, or it can be a simple disc with the team’s colors.
The pit crew who held up the lollipop was named “lollipop man”. However, since 2013 most F1 teams use an automated light system to perform the task of lollipops.