How do I create an image with blurred background and focused foreground?
This background looks like it was created with the Lens Blur filter in Photoshop, with a high radius and with specular highlights set to 0. Shape Blur could also get this effect, using an elliptical solid shape. It doesn't look like in-camera blur, and it certainly isn't gaussian blur.
The hand with phone and the face of the phone are separate images composited together, which were then composited onto the background, making it easy to adjust and blur the background to fit the needs of the composition, which also suggests that the blurring was done in post.
Either way, it's very important to add noise after the blurring, which wipes out the noise, so the background looks like it belonged to the foreground. (Actually, the designer in this case overdid it slightly. The background has more and different noise than the hand so that they are subtly, visually disconnected by that as well as the lighting. That's what gives the overall image its artificial look.)
If this was a smart designer, the noise was added by creating a 50% gray layer in Overlay mode and running Filter > Noise > Add Noise, with Uniform and Monochrome both selected.
Ideally you'd be taking the photo using a lens with a shallow dpeth of field to bring your foreground into focus but nothing else.
To fake it, you need to spend some time masking out your foreground, then applying various degrees of gaussian blur to the rest of the photo.