An audience exclusion tells an ad platform not to show your ads to a specific group of people. In Google Ads you can exclude audience segments, including a Customer Match list of your own disqualified leads, so budget stops being spent on people you have already decided are not worth reaching.
Excluding is not the opposite of targeting
Targeting picks who is eligible to see your ads; exclusion carves people back out of that pool. The two work together. You might target an in-market audience while excluding your existing customers, your disqualified leads, and irrelevant placements. Exclusions are where a lot of quiet waste gets removed without touching your core targeting.
The highest-leverage exclusion in B2B
The one most accounts never set is a Customer Match list of leads the sales team already threw out. Once uploaded, apply it as an exclusion so those people stop clicking your ads on your dime. It sits alongside negative keywords and placement exclusions as a standing hygiene layer. The full tactic is in stop paying to re-acquire leads your sales team already rejected.