It's a vector graphic and the style called Flat Design. You can create this kind images in Adobe Illustrator (in photoshop, too).
There is two kind of design trend in web. Realistic (skeumorphic) and Flat design. In realistic design there is too much gradients, shadows, highlights and it's looking realistic. In flat design you don't need too much shadow, gradients etc. You can check www.flatvsrealism.com to understand it well.
And also there is a trend by Google named Material Design. It's almost same thing with flat design but it has standards for motion, shadow and color palettes.
You can find much more when you google "Flat vs Realism" or check the links below: