Ad Group is a grouping of ads, keywords, audiences, or assets within a campaign.
It matters because paid search can spend budget quickly. Knowing this term helps teams control intent, targeting, bidding, creative, conversion tracking, and lead quality instead of optimizing for surface-level clicks.
Example
A garden supplier places greenhouse kits and greenhouse accessories in separate ad groups within one campaign. Each group uses ads and landing pages relevant to its products, making it easier to review whether a particular offer matches the searches attracting clicks.