I like this question because it offers an opportunity to dig back into my personal history and try to figure out where my first exposures to gaming came from. Perhaps unsurprisingly my first exposure to gaming came from family. The first video game I can remember playing was Joust with my cousin on his NES. I want to say that it was at that moment that my love for gaming crystallized, but truthfully I was so young that my memory of it is foggy. The next memory I can conjure up was getting bootleg copies of Warcraft 2 and Doom from my father's co-workers.
Not to endorse bootlegging or copyright infringement, but I can safely say that those illegal copies sparked my love of gaming. Soon after I was first exposed to the magic of Star Wars at my grandparent's house and to nerdvana I was off. In short, a variety of influenced cemented my love of all things geeky.
That answers the "How?" but inside the question of "What" in this context is also a "Why?" I've always been an imaginative type. I spend my free time thinking of fantastic settings and stories, and I used to draw a great deal. Gaming was a natural outlet for that what with most of its content set in far off and mystical places. I got to explore worlds alien to our own, even if at the time they were in 2D through beautifully rendered pixels (wtb house on the floating continent of Zeal). I'm a gamer because I'm a dreamer, and gaming has always been where dreams come to life.
There is of course one other factor. I have always been a shy, socially awkward, nerd. Two decades ago when I was first exposed to gaming it was the haven of people just like me. I found friends who felt as I did and enjoyed the things I did. There were others involved to be sure, but it certainly attracted a disproportionate excess of types like me. But as I have grown up so has gaming, and right now it's undergoing a renaissance where we learn to cherish those who have always been here but were never as prominent or perfectly fit that mold, and create a medium that invites new people to join. I think gaming is better for it.