What is a trading desk?
A trading desk is an easy to use all-in-one interface or platform, which allows you to purchase display advertisement such as banner advertisement and digital video advertisement on various advertisement exchanges and advertisement networks at the same time. Trading desks bundle all of this inventory into one large inventory supply platform, that has access to a vast array of smaller supply sources and hence allows a much larger reach than buying digital ads in smaller ad networks.
Those purchases or transactions are handled on a real time bidding (RTB), also called programmatic buying, basis. This means that you are not buying a package of advertisement impressions to a fixed CPM price, but that each bought impression is seen as an individual purchase.
The advantages of this system is that you have full price control and a highly increased possible reach. We are listening to the stream of around 50,000 different users per second, that are 4.3 billion possible impressions per day for your advertisement or online media campaign. Buying real time bidding inventory in that manner is the most affordable way to purchase online advertisement also, as you can limit the maximum price that you want to pay, but as well get impressions at a much lower price point.