LearnDash is the learning management system that a lot of WordPress course sites are built on. It turns WordPress into a place where you can create courses, split them into lessons and topics, add quizzes, and sell access. The course builder is drag and drop: you arrange lessons in order, set prerequisites so a student has to finish one lesson before the next opens, and drip-feed content over days or weeks. Quizzes support several question types, with timers, question banks and certificates that are issued when a student passes. There is a focus mode that hides the site header and sidebar while a student is working through a lesson, which keeps the page clean. It works with WooCommerce, Stripe and PayPal for selling, and with membership plugins if you want to sell access by subscription. Groups let you sell a course to a company and let them manage their own learners. If you want to sell a course from your own site instead of a platform that takes a cut, LearnDash is the standard choice.