X-Ray is a set of tools that helps you with look dev and rendering.
right now it consists of two main areas, real-time rendering and multi-layer texturing.
Realtime Rendering:
it’s important to know that x-ray is not a render engine, x-ray uses the render engines
you already have in Maya and use them to achieve real-time rendering in Viewport 2.
Texturing:
Easily doing multi-layer Texturing, this part is not limited to real-time rendering, you may
use it for texturing an object for use with V-Ray or Redshift
Focused on being Artistic
X-Ray is not using any special physical-based light or shading technique, instead, it is focused on being more artistic as you control things like light and reflection unlike any other rendering tool