An insertion order (IO) is a document that is used in the online advertising industry to outline the terms and conditions of an advertising campaign. An insertion order typically includes details such as the advertiser, the publisher, the ad format, the ad creatives, the targeting criteria, the pricing model, the delivery schedule, and the performance metrics. An insertion order is used to formalize the agreement between an advertiser and a publisher, and to ensure that both parties understand and agree to the terms of the campaign. An insertion order is often used in conjunction with a contract or purchase order, and can serve as a reference or record of the campaign. An insertion order is an important tool for both advertisers and publishers, as it can help to facilitate the planning and execution of an advertising campaign.