What is Google AdWords Double Serving policy?

In order to make the auction process fair and to avoid abuse in ad networks, Google has discouraged advertisers from running ads for the same or similar businesses across multiple accounts triggered by the same or similar keywords. This policy is known as 'double serving policy' and Google has strictly prohibited multiple ads from the same company from appearing on the same search engine result page. It curtails the problem of displaying more than one ad and users can see ads from different companies in one SERP.