Google has launched a remarketing product with similar functionality to what the other big remarketing providers offer (Acerno, Dotomi, Advertising.com, etc). The technical implementation is about the same. A Google pixel needs to be installed on the advertiser’s website 
which facilitates the remarketing. When a visitor comes to the website and leaves without taking the desired action (buying, inquiring, etc), the person will be subsequently shown display (or text) ads in an effort to lure the person back to the site. These ads will follow the person around the internet provided that the sites they visit are within Google’s network. The size of Google’s network is on par with that of the other big ad networks, so from an audience perspective, the reach is competitive.
The way Google has chosen to price this product, however, sets it apart from the other remarketing providers. Google’s structure is CPC, whereas the other companies charge CPM or CPA. Cost-wise, the CPC model has a clear advantage. Comparatively, the cost savings to the advertiser can be huge.