A typical onboarding session is a block of time, usually 1 or 2 hours, where a specialist or subject matter expert will guide you through the basics of using a new software or system.
This is almost the same, except there's no live person with you. Arguably, what's here is better! Over 50 lessons using video and text that you can watch or read as many times as you like. There's no restrictions on the number of hours you use up. No need to book a time slot.
No, you don't need to know any of these technologies. However knowing something about them will be an advantage. Understanding basic formatting will help in following along with any code examples in the courses but each section will be clearly explained when necessary. For the complete novice, there are step by step instructions on exactly what to look for in the Power Editor and what to copy/paste where.