The main difference between a flyer and a poster lies in the size, and from there, in its usefulness. Thus, flyers have a much smaller size, and are designed to be hand-delivered to people who circulate on the streets; while posters have a substantially larger size, and their function is to be posted at strategic points in the city to serve as fixed advertising. Thus, both flyers and posters allow to advertise a certain good or service, but one is delivered to consumers directly, while the other is placed in a fixed place.
