I take it as what the name means. To write with light.
Under that you can do various things like capture and image on a recording media. Or project a laser light show. In the olden day I took "Photographic Science and Engineering" at Rochester Institute of Technology. This was a degree program that was not about taking pictures, but delved into the chemistry, optics and physics of what happened before, during and after you pushed the button.
As part of the curriculum we took courses that were designed to make us well rounded individual. One was a course in fine art. I actually liked it. We had to do three art projects as part of the course. We could not use photography as the professor informed us tat photography was not an art form. So if a professor at the world's leading school of photography says that photography is not an art form, it must not be an art form.
Actually photography is more like welding or painting. You can create a sculpture or build a bridge by welding. You can paint your living room or a make a painting called Starry Night. Not all of photography is art. I would argue that it is the least used purpose of it. Most is documentary. It records the moments of our lives. Or wars. Or protests, or sporting evens etc.
I do think that photography opened the door to the modern art movement. By freeing "artists" from having to accurately record their subjects on an easel, it allowed them to look at the world around them in a whole new way. I don't think that impressionism, cubism or the other art forms would have developed without photography.