Negative keywords can help advertisers better target their ads by:
- reducing their campaign’s daily budget recommendations
- raising the average position of their ads
- increasing the number of relevant Display Network placements
- reducing the number of irrelevant clicks
One key to a highly-targeted campaign is choosing what not to target. Because keywords can target a broad set of phrases, it’s important to see whether every term is related to your business
Negative keywords let you exclude search terms from your campaigns and help you focus on only the keywords that matter to your customers. Better targeting can put your ad in front of interested users and increase your return on investment (ROI).
Read more here: https://support.google.com/google-ads/answer/2453972