How does fashion photography work?

The most generic way to answer such a vague question is this. Fashion photography works by finding the best methods to photograph fashion in order to make it the most presentable and/or to give viewers the sense of practical usability in real word scenarios. There are different lighting techniques and different goals that in other forms of photography. For example if the texture of a certain garment is its selling point, then a good side angle on key lighting may bring out that texture by creating miniature shadows in the texture to sharpen it. A bit of fill hair lighting to make the model pop and there you go.