What size/kind of lens was this photo taken with?

I want to buy a lens for my nikon that can do these kinds of photos

EXIF data says this was taken with a 50mm lens, at f/2.8.

So, 50mm prime lens, f/1.8 or f/1.4 (if you can afford it).

Definitely 50mm. Not sure if 1.8 or 1.4. EVERY photographer should have a 50mm lens in his or her camera bag. They're fast, light, and produce sharp images.