Reflection vs Gloss

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).