I too am fairly new to the C5 hobby.
I do a lot of research on the web and have found the C5 to have great resources due to some very generous and knowledgable fellow owners. - thanks!!
That said, I too have come across the variations in "top" terminology. I have the Y2K coupe with the 2 top option, so I have a start point. One top is what I call the "winter top". It is the heavy painted/ padded one. The other one is the "summer top" it is much lighter, heavily tinted blue translucent plastic. You can somewhat see through it but it looks black. At first I thought it was black, maybe brown, until I read about the Blue plastic tops. I took a good look and indeed it was blue. Kind of like the sky??
Here's the thing - the plastic top is sometimes called clear or glass or clear glass, and it is none of those. However I think it has its roots in some of the original "T" tops, especially the 2piece C3 that were actually glass. Those were smoke, clear and silvery, and others. Additionally some aftermarket companies may make up a clear unit, but it is not real glass. Go figure??
NEXT - what is the proper treatment for the plastic to avoid UV. I have seen some nasty ones!!