A demand-side platform (DSP) is a type of ad tech platform that is used by advertisers and ad agencies to manage and buy advertising space. It is called a "demand-side" platform because it helps advertisers to manage and execute their demand for ad space, by connecting them with publishers and ad networks that have available inventory. With a DSP, advertisers are able to target specific audiences and set their own terms for buying ad space, such as the price they are willing to pay and the type of ads they want to run. The DSP then uses algorithms and data to match those terms with available ad inventory from publishers and ad networks, and helps to automate the buying process. This makes it easier and more efficient for advertisers to reach their desired audience with their ads. In the ad tech industry, DSPs are often used in conjunction with supply-side platforms (SSPs), which help publishers to manage and sell their ad inventory.