Question: Why does black glass reflect better than white glass? Both of them are glasses, so they reflect light. But why black glass reflects better?

See below, shiny black glass.

![enter image description here](https://i.stack.imgur.com/wizCT.jpg)

Answer: 
You may be confusing reflectivity with contrast or other effects. When we look at a reflection from a shiny black surface, our eye/brain adjusts for the image darkness and retains the colors. Reflection from a white surface gets (I think, not absolutely sure here) overloaded with the underlying diffuse signal and it's harder to discriminate.
Glasses primarily transmit light, but part is also reflected, so that they are characterised by a number, reflectivity (or reflectance), while the transmittance is related to it by complementarity (the total intensity must be conserved, although part of the light might even be absorbed or interfere with itself and cancel out). Dark glasses are usually treated with coating (like an anti-reflex coating) that change the value of the reflectivity