Glad you asked. The words "Walk-Ins" derives from "Drive-In" movies... where people used to drive to an outdoor theatre and watch movies in their cars. It started because a few neighbors wanted to enjoy movies outside under the stars, instead of inside on our TV's. Eat popcorn? Yes! Hang out with friends? Yes! Who wants to be stuck inside?
Walk-Ins generally occur in a neighborhood, warehouse district, park, or other casual setting. The movie is projected outdoors on a wall or some other backdrop. An important part of the Walk-Ins is that there's *no charge* to attend. Completely free. By the peeps, for the peeps.