Can someone explain the difference and uses between a glossy image texture and a reflection texture? Do both plug into the roughness input?
the data in a glossy texture usally shows how glossy a material is,from 0-1.
with a color invert node,between glossy texture output and roughness input, you can make it to a roughness texture.
i think with reflection texture you mean a specular map?blender dont use a reflection map,you can use specular in the principled PBR shader.but if you have a real reflection map, you could build a custom node setup for this easy,for masking or percent use ie, with a mix shader and a glossy shader.
in general, a glossy/roughness map shows how glossy/rough the material is .
a reflection map,in theory shows how reflective the material is.from 0-1 reflection (from zero reflection to full mirror like reflection).
Your explanation is still not very clear if im honest. If find the naming convention confusing in blender.
Unfortunately nick has not written from what source engine or workflow he was talking about the reflection texture.Maybe he means a reflection value map as described,or a metallic map,who knows.
It is a difference if you have a reflection map or a spec map.Reflection map typical represents the amount of reflection.The spec map as you know is based on IOR.
A glossy map however, is widely known that can be inverted to a roughness map.
Here in Vray you can see as example how a reflection map can be used (Base layer parameter → Base reflection).In short,how much the reflection is mixed in.