This is a topic I’m personally very interested in and have done a fair amount of study on, so I wanted to chime in with one thing that I hope will be helpful: introversion is not the same thing as shyness.
As measured through psychographic assessments like Myers-Briggs (full disclosure: I’m an INFP but just barely on the “I” - almost dead center between Introvert and Extrovert, the so-called “ambivert” zone), introversion and extroversion refers to whether you find social settings/being alone to be mentally regenerative or mentally taxing. Extroverts tend to get manic, stir-crazy, etc. when alone and crave social interaction as compared to introverts; introverts tend to find social situations draining and need more ‘alone time’ than extroverts.
This is different from shyness, which generally refers to someone’s comfort level and readiness to engage interpersonally face-to-face, especially with strangers. The face-to-face part is important, because I think we all know people who would be described as “painfully shy” in person but who are very ready, willing, and able to interact online.
Because they are different things, this means that you can have gregarious, outgoing introverts - they have very good social skills, they just can’t keep it up for long stretches without getting drained by it. Conversely, there are shy extroverts - think about the people who are always up for group activities, but don’t actually talk very much when they’re in them.
Whereas introversion/extroversion is thought to be more hardwired or intrinsic, shyness is more malleable - and something that people can even work to improve. One of the great things about college - and especially residential colleges full of high-achieving kids - is being exposed to a much greater diversity of people and opportunities than were available in grade school. That’s something that helps put people at ease and provides a sense of belonging, alleviating some of the factors that go into shyness. As a result, even those who are very strong introverts often become less shy in college! That was certainly my experience at Georgetown.
And to echo what has been astutely pointed out already - as much as we are all to some extent ‘performing’ when we put ourselves out there and interact with others, that goes quadruple for social media. Also, because not face-to-face, many introverts and shy people find it much easier to be social and engage online than in person. Don’t sweat it!