A DSPs (Demand Side Platforms) is an ad systems that represent the interests of buyer (advertisers) whereas SSPs are platform represent the interests of publishers.
You will not find any inventory on a DSP
The combination of SSP/DSP can be considered the counterpart of ad networks.
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, DSP’s are differentiated from ad networks in that they do not provide standard campaign management services, publisher services nor direct publisher relationships.
DSP execute your campaigns
Mobile Web:
Mobile App: