Campaign, Ad Set, Ad

Quora splits every account into three levels: campaign, ad set, and ad.

The campaign holds your objective and top-level budget. The ad set is where you set targeting, bid, and schedule. The ad is the creative people actually see. One campaign can hold many ad sets, and one ad set can hold many ads, so you change one variable at a time instead of rebuilding from scratch.

You run one campaign on the Traffic objective. Under it you build two ad sets: one targeting a list of software questions, one targeting a broad topic. Each ad set carries two ads with different headlines. That is one campaign, two ad sets, four ads, and the dashboard tells you which targeting and which headline won, separately.

Do not stuff every targeting idea into one ad set. If topic, keyword, and audience targeting all sit in the same ad set, you cannot tell which one drove the result. Split them across ad sets so the dashboard answers the question for you.

One variable per ad set, or you learn nothing.