Photoshop(PS) is mainly used for image processing and effects. For example, those large-format color advertisements on the right need to be processed by PS, and if necessary, they can be edited by CORELDRAW.
It can be said that the two softwares complement each other. Of course, you can also do it alone with ps, but the process will be more complicated.
Skills and functions, if you are not familiar with these two softwares, there is really nothing to say, but you can learn them quickly. Go to a crash course, it is estimated that you will understand in 2 months. If you are familiar with it, there is only one skill. Read more, study more and do more. You can see what your peers are doing. Simply put, it is plagiarism.