How to make an image transparent?

Question

Design

I don’t know what it’s called, but how to make the very first inner page like on this design. Tama picture of the city in such an effect! In photoshop!
Picture

Answer 1

And what is the actual difficulty: put a picture of the city, and on top of it or opacity or gradient or semi-transparent background

Answer 2

create a layer above the image layer, fill it with the desired color, set the opacity to ~ 50%

Answer 3

Set the blue background to transparency. In Layers.