Demand Gen is a Google campaign type that runs visually-driven ads across YouTube, Discover, and Gmail to create demand among lookalike and interest audiences. It replaced Discovery campaigns and is Google's answer to paid social.
What it is for
Demand Gen targets people who are not searching yet, using image and video creative across Google's feed surfaces. It is built for the top of the funnel, generating interest rather than capturing existing demand, and it leans on audience signals and lookalikes rather than keywords.
How to judge it
Because it is demand creation, judging it on last-click CPA will make it look weak; it should be measured on the demand and searches it generates downstream. It is a different job from Search, and holding it to a Search yardstick is a common way teams kill a working top-funnel channel.