The small, light posts are called typically called traffic poles, at least around here. A bollard is a heavy, strong thing made of concrete or metal. The poles are meant to direct traffic and to gently deter drivers from crossing them. Bollards are intended to stop vehicles dead without giving a shit how much damage they cause.

Poles can be very good for traffic when used correctly but sometimes street planners make mistakes. Either that or people insist on going against what the poles are suggesting.