What is Google AdWords Remarketing?

Remarketing is the process to connect with the people who previously came to your website or Mobile App but not taken any action.

So in Adwords we can target those audience to display our Ads. It will increase the purchase and brand awareness. 
As this group of audience will be familiar with your brand so it will take less efforts to take valuable action.

It is also known as Retargeting that increase the ROI and conversion rate.Using remarketing, you can show Google ads to your previous site visitors while they browse the vast number of Google partner sites in the Google Display Network.
By targeting more narrowly, you can therefore increase ad relevancy and lower your cost per click.