Video Games are games played on a screen, instead of, for example, board games, card games or games that involve actual physical movement. People who play a lot of videogames are known as "gamers", "nerds" or "virgins".
The first videogame know to man (or wikipedia in any case) was a device called the Cathode-Ray Tube Amusement Device patented in the United States in 1947 by Thomas T. Goldsmith, Jr. and Estle Ray Mann, two people with absolutely no talent for coming up with cool names. It simulated a missile firing at a target using 8 vacuum tubes and some targets drawn on an overlay, so it sounds more like something McGuyver would make to entertain his retarded nephew.
And it looked like a broken traffic light.
Over the years, some more devices were made that could only be considered videogames in the broadest sense of the word, so aren't worth mentioning here. Let's just fast-forward to a game anybody still alive today is able to remember: Pong. It featured two paddles and a ball and was so boring that these days people even refuse to play it during load times.
Then there were devices like the Atari 2600, the Commodore 64 and then the gaming industry crashed because nobody figured out it was a bad idea to produce more pacman cardridges than actual consoles. Let's just skip to Mario.
Mario first appeared in a game called donkey kong where he had to jump barrels and save his girlfriend, before getting his own game on the NES in which he randomly entered castles full of lava, flames and firebreathing dragons, because checking if the princess is actually in there first is for pussies.
But fuck me if I'm going to tell you which castle!
Sega responded to Mario with it's own mascott, a totally badass (by 80s standards, that is) hedgehog, whose only skill was he could run really fast. So he was pretty much the video game equivalent of a Jamaican.
Fast forward a few years, and Sony introduced it's Playstation 1, 2 and 3 (Goldsmith and Mann were pretty creative compared to Sony), Microsoft it's Xbox and Nintendo lost interest in making videogames after some bad results with the N64 and the Gamecube and launched the Wii and a shitload of partygames.
What gamers look like, according to Nintendo
At present, Nintendo is forking in lots of cash by shifting their target market to superhip young adults and your mom (insert penis joke here), and Microsoft and Sony's gaming devision lose millions each year, while kids today still refuse to play outside.
All gamers look like this. If you've never seen one, it's because they don't come out much.
Gamers are people whose lives pretty much revolve around playing and talking (usually complaining) about videogames. This has gone so far that they actually started referring to themselves and all their videogame-related forms of expression as "gamer-culture".
One particulair form of "gamer culture" is the videogame webcomic. This phenomena is widely believed to be started by two guys who lived together and played a lot of videogames, and thought that'd be interesting enough material for a webcomic.
Copyright Penny Arcade. but who cares, these things are all over Google image search.
It turned out they were right, as their readership right now is in the hundredthousands and the web is littered with other webcomics made by people who think it's hilarious to draw Luigi having sex with Princess Peach.
While gamers don't generally favour a distinct music genre, they do like to play, or listen to videogame tunes on different instruments. Mostly the Mario theme.