What are the main post-production of photography? Do they just use PS to deal with defective pictures?

After photography, you mean after photography, right? Not the same as the rear camera.

In this later period, you usually talk about PS, which is not only used to deal with defective pictures, but also used to adjust colors or put them together, and of course, layout design. . . Now there are many professional image processing software, such as PS AI, and some fool software, such as Meitu, Xiu Xiu, Light and Shadow Magician and so on. These can make some photos of your own life, simple but practical, but to achieve very advanced results, it is recommended to use professional PS.

I hope it helps you.