DDG stands for DuckDuckGo, a search engine that does not track its users.
Google tries with all its might to track everything you do via their google search engine, YouTube, google maps and their mail (gmail) and other services they own.
Of course all of that knowledge is used in targeted advertising for now (but who knows for what in the future). Google is first and foremost, an advertising company. The technology is a tool.
The same goes for Facebook via their services. They've acquired WhatsApp and Instagram too. All those conversations and photos are on their servers.
A huge repository of data that google and Facebook are mining to turn into information about us. We are the product.
One recent example of how this can be so powerful is what happened during the U.S. elections and the involvement of Cambridge Analytica.
That scares me, but not everyone is concerned. That's ok too. To each his own.