DSP is Demand Side Platform which is also called as buy side optimizer s, and buy side platforms.
Demand Side Platforms provide centralized (aggregated) media buying from multiple sources including ad exchanges, ad networks and sell side platforms, often leveraging real time bidding capabilities of said sources. While there is some similarity between a DSP and an ad network,but DSP’s are differentiated from ad networks, like in that they do not provide standard campaign management services, publisher services nor direct publisher relationships.