No, I just like learning things. Especially things that lots of people misunderstand.

You just gave a good example of two of the major sources of confusion.

First, introverts get stressed out not by people specifically, but by high external stimulation levels. Stimulation is much higher with strangers, because the nervous system goes on alert, trying to detect possible danger, approval, etc. in the other person's behaviour. Whereas with close friends, the nervous system is relaxed, because you know each other well enough to not have to be paying close attention all the time in search of hidden cues and such.

Second, independently of introversion and extroversion, there exists social anxiety. Whereas introverts just get stressed by prolonged social contact with strangers, if you're actually afraid of it, that suggests social anxiety. As with introversion, it doesn't manifest in all social encounters, only ones where there exists the threat of being judged or screwing up in front of strangers. So, like introversion, it isn't triggered by spending time with close friends. There are numerous causes for it, some genetic, some due to upbringing or bad experiences.

And yeah, the internet changes things, because the pressure of face to face contact is gone. Much of the stress for introverts and fear for the socially anxious is caused by nonverbal communication, which is absent online. That's why both groups are overrepresented among internet users.

To find out if you're introverted or extroverted (keep in mind it's a spectrum, it's possible to be in the middle or only slightly towards one side), you have to think about what drains you of mental/emotional energy (I don't know how to accurately describe it), and what charges you back up. Do you often get stressed out from being alone and need to meet with people before you go crazy? Do you get stressed out from being with people, and dream of spending time alone to recharge? Keep in mind, being afraid of meeting people is not the same as being stressed out from spending time with people.

To find out if you have clinical levels of social anxiety (subclinical levels are common, many people feel some anxiety when meeting someone new or speaking in front of an audience), you have to think about whether it gets in the way of your life. Do you just get stressed out a bit when meeting strangers, but still do it anyway, or do you actually miss out on potentially beneficial new acquaintances because you're too afraid of meeting them, or refuse good job opportunities that require frequently interacting with strangers? If it's the latter, contacting a mental health doctor is probably a good idea, it's no good to constantly miss opportunities in order to accommodate the anxiety. It's usually treated with talk therapy (CBT), with medication available for those who refuse or don't respond to the therapy.

And while I'm on the topic of misunderstood concepts of social interaction, I'll leave a few words about the autism spectrum. It's separate from both introversion and social anxiety, and describes the extent to which an affected person's brain has the parts that process nonverbal communication underdeveloped. Since those parts are specifically formed to be very effective at it, and the rest of the brain is not, when they're underdeveloped a person can't process body language, social cues, gestures, tones of voice, etc. at full speed. As soon as such a person becomes old enough to realize that they're constantly screwing up in social situations, they're almost certain to develop social anxiety. And since there isn't any nonverbal communication to worry about online, autistic people are another group that's overrepresented among internet users.

It's worth noting that autism often doesn't come on its own, but together with other neurological disorders, such as ADHD or OCD, and most annoyingly, various intellectual disabilities. That last bit is why "autistic" has sadly become a general insult with roughly the same meaning as "moron", even though it simply means "unable to process nonverbal communication". On the other hand, sometimes the neurological screw-ups result in another part of the brain becoming more developed, resulting in the rare "savants" that autism is associated with, or just some sort of hypersensitivity, which might be useful or detrimental.