Have you ever tried to shine sunlight through a prism? Or have watched a rainbow?
Both split solar radiation into its component parts, spacing each part next to another. There is short-wavelength - violet - radiation on the one end, and long wavelength - red - on the other. Those two, and all the colours of the rainbow in-between correspond to energy levels that can interact with, and therefore be detected by, the chemicals making up the structures called "rods" in our eyes.
But there are more bands past violet and past red. This is somewhat less true of actual rainbows, as a multitude of optical effects conspires to muddle the issue, but in principle it's true.
Ultraviolet (literaly "over violet") and infrared ("under red") are the names of the first bands of the rainbow that human eye can no longer detect.
Incidentally, various materials are transparent to various wavelengths and opaque to others. As it happens, UV is blocked by glass, so whenever you see a pair of glasses made of actual glass and not plastic with a "UV filter" sticker, you can be sure that there is no actual filter other than just the regular glass they're made of. Whether it's the same with plastic glasses I don't know, but wouldn't be surprised at all if it were the case.