Design 101 is a beginner-level course, so there's no prior knowledge required.
You'll get a meaningful intro to graphic/visual design concepts and you'll develop a much firmer understanding of design principles — primarily by practicing with real projects (which is really the key to improving your skills). You'll get regular feedback from a mentor on your project work, and you'll Skype with them during the course as well. By the end of the course, you should have a much stronger sense of your own design skills and what you'd like to focus on from there if you want to proceed further (we have additional courses on UI/UX, as well as more intensive options like this bootcamp).
Take a look at some examples of past student work in Design 101 here and here.
If you don't already have basic knowledge of design tools like Sketch/Photoshop/Illustrator, we have intro units that cover the basics there, and you'll gain further proficiency with those tools through the project coursework.