DPI in Photoshop?

Question

Adobe Photoshop

Good day to all!
I'm learning photoshop and I'm faced with this problem, how to make this quality in a picture?:

As far as I know, it's something called "DPI".
And how to make the same background as in the example above, only here:

Answer 1

You have a clearly too high DPI, try reducing it to 72 and below. And the graininess itself is an effect or a filter. In fact, this is Noise. Noises. You can also achieve this or a similar effect by sharpening.