UV/IR stands for ultraviolet and infrared, and generally refers to UV/IR cut filters. A standard camera is sensitive to the visible light only (like our eyes), because it blocks the wavelengths at both ends of the visible light spectrum (UV and infrared).
However, some astrophotography cameras – called full spectrum – do not block these wavelengths, in order to increase the global sensitivity to light. It is especially useful for stellar objects, which can also be photographed in infrared or ultraviolet, thus providing additional data.
For these cameras, an UV/IR cut filter can be necessary to revert the camera to a normal mode, and capture only visible light.