A contest is generally a competition allowing participants to win prizes. In marketing terms, it is a promotional technique. Indeed, in order to participate in a contest, people are often, in a way, obliged to buy the organizer’s products.
If a contest is held by a magazine, interested parties usually have to purchase the magazine to find the entry form. If it is set up by a central purchasing agency, participants will have to present a receipt from one of its affiliated stores. It is therefore a way like any other to sell and talk about the company.