How do ya make your background all "blurry" like that

is a question I get a lot.

That blur is called bokeh. The word "bokeh" comes from the Japanese word "boke" (pronounced bo-keh) which literally means fuzziness or dizziness.

Look for points of light in the background. Perfect subjects for this are distant points of light at night or sometimes light shining through leaves or specular reflections in daylight.

All bokeh are NOT equal. Some people are very very bad at it, actually! I strive really hard to get my bokeh on target.
If they all blend together nicely, that's nice bokeh. If they are perfect little circles, then that's neutral bokeh, not too bad, but not the best. If they are all swimmy and look little donuts, then that's bad bokeh.
If they are perfectly round in the middle of the image and oval or lentil shaped at the sides that tells you the image was probably shot at full aperture.

In order to change your aperture, you need to first learn what it is....

More than I am going to get into today, but I will say, if you are interested in me emailing you an awesome natural light tutorial, let me know, I will fwd it to you.