Stair Treads can be designated as the section, made for taking most of the wear and tear and had to be solid enough to handle that for a long duration of time. People use to cover there staircases with carpet; just to make it last longer. Now a days the trend has changed and if we are looking indoor staircase than plenty of options are available,and the most widely adopted one is the wood treads polished and seasoned to last longer. Prefabricated exterior stairs doesn’t have that many options, since the exterior use make it more vulnerable and no one wants to invest highly on this, just to see that it will last few seasons only.
Stair Treads and risers define the entire structure of the staircase and provides the face to the staircase keeping in mind the limited space and the type of staircase required. I would personally suggest that one should first select the treads and risers and than finalize the shape of the staircase, because not all materials look good in whatever shape you want them too. Glass staircase, a new trend generally has only treads and no riser section, they are open from the back; but you can also get the customized version with the risers.
Wood Stair tread has been the trend since decades now and it is just that the variety of wood has increased from the past few years. Now you have more variety of Mahogany, Red Oak, Walnut, Brazilian Cherry and many more if you want to get that in a totally different wood type. Now these materials are easy to install and easily available. I would suggest you to get a stair railing and the stair stringer of the same wood type, the combined output will enhance the interior of your house. Glass is only used if the walls are of glass and have a matching aesthetic in glass and if you want to go ahead with the glass staircase than a best decision would be to go without glass risers.