Google Adsense and DoubleClick Doubts

Hi everyone
I need some help to clear my doubt. I want to know are Adsense and Doubleclick separate companies or both are same?
I have seen Doubleclick ads on a few websites and when I searched, I found Doubleclick has been acquired by Google long time back.
But Doubleclick has different website and allows people to put ads on their site.
So please tell me, whether we can have both Adsense and Doubleclick ads on same page or not?
Thanks.

See original post by Vishal Gupta