Real-time bidding (RTB) is an automated, real-time advertising auction system that allows advertisers to compete instantly to display targeted ads. When a user visits a web page or uses an app, an ad impression is auctioned on a dedicated platform, and the highest bidder displays their ad. This process optimizes campaign relevance and effectiveness by adjusting bids based on criteria such as cost, context, and audience profile. Initially used in online advertising, RTB is expanding into digital traditional media, offering greater flexibility in purchasing advertising space.