Microsoft just dropped the new Clarity Boost feature for xCloud, and it's exclusive to the Edge browser. What sounds like a buffing spell that your party's cleric might cast on you in an RPG is actually a set of proprietary optimizations designed to make the game streaming experience just a little bit more visually impressive.
Players streaming Xbox games via the xCloud service on Edge can now activate Clarity Boost, which focuses resources on scaling improvements to make visuals sharper and more detailed. In the official release announcement Microsoft provided a comparison image from Gear Tactics that... doesn't really do a good job of demonstrating the improvements, but luckily users have already posted their own which make the difference more visible.
Essentially, we're looking at a fairly minor reduction in blurriness and increase in texture resolution, by the looks of it. Clarity Boost is client-side, so it optimizes the output to your display ensuring that streamed content is scaled in a way that reduces quality loss as much as possible.
Based on some tests in games like Forza Horizon 5 and other recent titles, the changes can be best noticed in small details, mainly on surfaces. Materials are higher resolution and more detailed, faces are clearer, foliage seems sharper and more realistic. It isn't a groundbreaking improvement to be honest, but these small boosts sure add up.