Real-time bidding is a new and dynamic way to buy online media. Through an automated process, media buyers can evaluate, bid on and purchase ad inventory on an impression-by-impression basis. With real-time bidding, media buyers can drive meaningful one-to-one connections to consumers with greater scale and efficiency.
Every time an impression is available, the advertising exchange "asks" us if we'd like to bid on behalf of an advertiser (the "bid request"). You get a variety of information, such as the site the impression is one, the time stamp, information about the user, etc.
You typically have milliseconds to respond with a bid (the "bid response"). What you bid is entirely up to you. You don't have to bid if the impression is not valuable to you. If you win the impression, your creative is served.