There's two different things we call waves because they have similarities. The wave you are thinking of is a behavioral pattern of matter, like water. This is a word to describe the motion of something else. A wave of light isn't motion of something. It's an actual thing itself, that when viewed through a sensor, moves in a wave-like pattern, so we named it a wave after the waves of the ocean. It's radiation. The difference between light and radiation that's invisible is simply that our eyes didn't adapt to see the invisible radiation. When people say infrared light, they are talking about radiation that has a lower frequency than what our eyes pick up, and when they say ultraviolet light they are talking about radiation that has a higher frequency than our eyes can pick up.