Think of retargeting a bit like internet stalking.
If a persons goes and views an Ad or product on a website. The Ad network responsible for displaying that Ad then places a cookie on the persons computer.
When that person carries on browsing different websites that Ad seems to follow them around even when viewing totally unrelated websites.
That is an example of Ad retargeting.
Google AdWords’ term for retargeting is Remarketing
Synonyms:
Remarketing