DuckDuckGo is search data is actually based on search APIs from major search players like Yahoo, Bing and Wolfram-alpha. In addition to these search APIs from major search vendors, DuckDuckGo also uses its own search bot call DuckDuckBot, to crawl the data. So what really make DuckDuckGo make so special and better search engine than Google.
1. Privacy Feature
DuckDuckGo does not collect, not even IP Address, User Agent, Cookie information and all sort of data being collected by other search engines. So what this mean in simple words, that no one can check your history when you are searching for something awkward and you need not to fear about someone controlling your search experience.
2. Big Bang
Yep, there is some sort of Big Bang Theory connected with DuckDuckGo. DuckDuckGo have feature call !bang which let you find result from specific group of website. Like apple !wiki will fetch you result from Wikipedia, apple !health will fetch results from health related websites, apple !tech will give you result from tech related websites and so on.
3. Instant Answers
Yep Instant Answers, the new feature which making Google a gaga again but it is the original creation of DuckDuckGo. DuckDuckGo fetch instant answer for queries like your favorite celebrity biography or age or something else from Wikipedia and Wolfram-alpha.
Now DuckDuckGo has completed its four years and host more than 1.5 million visits per day. Though you might think, DDG volumes are pretty low when you think of Google's one billion visits a day. But they have just started in such fierce competition, so it do take some time but with better privacy feature and clean interface, don't you want to give DDG, a try. And do tell me what you like about DuckDuckGo.