You would choose to advertise on the Google Display Network if you wanted to:
- show ads to people on non-Google search sites
- show ads on Google Maps
- show ads on websites related to your business
- show ads on Google Shopping
Google Display Network: – Google has its own Products like YouTube, Gmail, Google search and it also has Partners which are monetized with ad sense hence Google has a vast viewer base to show your ads to millions of people.
But Google always show your ads to websites related your niche or related business sites so you can get more related audience which is interested in your product. You can target audience according topics, interested audiences, demographics, and more to get maximize conversion.
Read more here: https://support.google.com/adwords/answer/6340468?hl=en