Being an introvert myself, one of the best inventions of the century is Moodle, where a good majority of courses are conducted online, and where introverted students can study and learn on their own in the quiet of their own room, away from the boisterous crowds of students in the classroom. Introverted students online are able to engage themselves when they feel they are able, and can also sit back from afar and take in the learning and discussions of other students while they form their own careful opinions.
In the article Online Learning and the Introvert, the author Lorelei Plotczyk notes that discussions online are all written on "equal footing" as the "playing field" is much more balanced than it is in the classroom. Everyone can be heard equally, and the shy and quiet students are able to have their time to reflect on their thoughts and their learning without feeling drowned out by the louder extroverted classmates. For the introverted students, this kind of learning often allows them to work to their full potential by letting them check their fear of participation at the door.
Although I am an extroverted instructor myself, I don't always find it easy to be front and center of conversations or groups. I can put on a great show of extrovert-ism, but it can be draining to the point that I am no longer able to be productive when I need to. Online learning allows the introvert in me to choose who I am, and when I am that person, and lets me contemplate ideas before I speak. So for me, online learning is not just about ease of accessibility to a course, but the ease at which I can learn that same material in the least stressful environment for me.