I was born in 2001, so I always grew up with a PC in the house, but I wasn't allowed to use it (nor would I have known how to) until about 2008. My earliest internet-related memories are of my father playing World of Warcraft while my brother and I played on the floor (he was a teenage parent, only 21 at that time, so being neglected in favor of WOW was a common occurrence.) Sometimes our parents would throw a party and use the computer for music. Other than that, I had no knowledge of how computers worked or what their primary purpose was, aside from the occasional day in school where the teachers would bring out laptops for us to do research-based assignments on. My classmates generously showed me how to play Minesweeper, Pinball, and a few MS DOS games (that were included on the school computers for some reason) like Oregon Trail and Odell Down Under, which I still enjoy to this day. My home PC was Windows XP, the school computers were still running Windows 98 at that point (2006-2008 or thereabouts) because it was a shitty underfunded school in Arkansas.
Around 2008 I saw my brother watching YouTube videos and wanted to watch videos too, but didn't understand how to navigate the site, so my father showed me how. My brother taught me the rest about basic computer-using/internet-browsing knowledge, like how to Google search, how to save files, so on. I was very into Pokémon (and other Nintendo franchises), dinosaurs, techno music, and some anime at the time, so I mostly used the internet to read about my interests or look at art related to them (and watch AMVs and flash animations, of course.) Around 2009, one of my favorite TV channels was 4Kids, and I went on the channel's website and noticed they had games to play. That led me to playing flash games and eventually to DeviantArt, Newgrounds, Kongregate, Armor Games, and XGen Studios. The 4Kids website also introduced me to Dino Run, a once-multiplayer pixel game where you played as a dinosaur, running from extinction and gathering points on the way. My username was "Kikiyo.Demon.Wolf", "Kikiyo" being a misspelling of Kikyo, a character from the anime InuYasha (which would air at 3-4 AM on Adult Swim - I also have fond memories of 8-year-old me waking up in the middle of the night and watching it) and the "demon wolf" part coming from a character I'd made up that was half-demon, half-wolf. I'd roleplay as this character in the chatroom, despite being, you know, a dinosaur.
By the time I was 10, I was getting into art and had a fairly good grasp on how to use social media/community-based websites. I made a DeviantArt account shortly after I turned 10 (with my parents permission! I was such a goody two-shoes back then.) to post my shitty anime furry art and follow other like-minded shitty anime furry artists (but all due respect, I loved those artists and they greatly influenced my development as a person.) As the atmosphere of the internet changed around the turn of the 2010s and the "wild west" feel turned into a "centralized social media" feel, I eventually settled on DeviantArt and Tumblr (which inevitably got me into fandom blogging about my interests.) I was on those two platforms on a daily basis until about 2015. I developed greatly as a person during those five years, from 10 to 15 years old, and despite the occasional drama I don't regret it, as the users of those sites introduced me to so many interesting things I likely would've never discovered without. I experienced the brony phenomenon, Gangnam Style, "superwholock", Homestuck, the beginning of the "post-trollface" meme era, hypebeast/swagfag fashion, obsessive Justin Bieber/One Direction fangirls, the beginning of the "SJW" era, aesthetic blogging, vaporwave... I'm also nostalgic for all of that, albeit in a different way. For better or worse, those sites as good as dead now.
I don't currently use any social media, assuming this website and anonymous imageboards don't count. I respect people's choice to use it, but it's just unfamiliar terrain for me. I've never used Twitter, Instagram, Snapchat, TikTok, etc., and have no plans to. Because leaving DeviantArt and Tumblr in 2015 was my equivalent of leaving social media, it felt like a chapter of my life closing. Now I just stick to my quiet corners of the web (whatever are left, thanks to internet censorship and the encroaching shadow of major corporations...) either talking to other 20-something's about our mundane-young-adult-in-2021 lives or reminiscing on the past like everyone else here is.