Programmatic is ultimately the automation of buying ads largely powered with data, which is primarily done through ad platforms. This is an extension of the traditional direct buys done over the phone or in a non-digital form as it becomes data driven & real time via an auction process the same you see on Google / FB. It is largely bought on a dynamic CPM basis. Personally for me, anything automated through an auction process for buying ads is programmatic, so search/social can by definition considered "programmatic" but is often grouped in its own channels because of some legacy things, especially bidding types where its still common to buy on a CPC basis. Ultimately everything is becoming programmatic. First it was banners (display), then it became video / Mobile App & now you see all emerging channels like audio / native / CTV / OOH all offer programmatic buying. The only things that aren't will be traditional offline pieces like print. Platforms exists within the programmatic world and are normally labelled as a DSP or a Demand Side Platform. Google has DV360 as their enterprise solution & is the largest DSP globally: imagine Google Ads but on steroids with more than just Google inventory / tools. Amazon DSP exists and is fast becoming no.2. Other popular platforms include TTD (The Trade Desk), MediaMath, Adobe Advertising Cloud & Xandr Invest. If you want to learn more about programmatic, aside from trying to understanding r/adops or r/programmatic , there are decent courses on the Google Skillshop (choose the GMP ones) and TTD made their Edge Academy free 2 weeks ago. That is actually quite nice in understanding programmatic if you ignore some of their sales push. Answer from goodgoaj on reddit.com