A professional (in the case of Google Ads, this means a Google Ads Certified individual) must understand a lot about not only your business but how to properly set up and maintain your Gooogle Ads campaign. They must have a solid understanding of which keywords to target and which to avoid. They also have to know how to track/monitor conversion rates, integrate call tracking, configure geo-targeting and create video ads. Once your ads are running, a professional will know which ongoing adjustments to make in order to ensure your ads are performing at their optimal level.