Programmatic advertising / automated advertising enables buyers and sellers of the ad inventory to automate the process. So, there is no need to contact the seller (publisher) directly. Theoretically everybody can run the ad, anywhere he wants and anywhere where his audience stays. Programmatic advertising is a natural continuation of former, so called advertising networks. You can watch the evolution of it here. Programmatic is divided into Open Marketplace (OMP, otherwise called Real Time Bidding (RTB)) and Private Marketplace (PMP, otherwise calle Programmatic Direct (PD)).
So, the equation looks like that:
Programmatic Advertising OMP + PMP,