The fact that you are reading this tells me that you already have a basic comprehension of what the internet is and how it is used. Most of you will also know that one of its many uses is to connect gamers from around the world in fellowship and competition. If you or someone you know is planning on joining the legions of online gamers, we'll go over some of the things you can expect.
Each of the current generation of consoles has its own online service; Xbox Live, PlayStation Network (PSN), and Wii's Virtual Console. Die hard fans of each debate the pros and cons of each system everyday. Honestly, each has its own ups and downs, and it is up to the consumer to decide in the end. The real point is that with each console, assuming you are connected to the internet (and have a subscription for Live on the Xbox) then you can join the online community. For more information on each console's specific service, see their website. But standard features include being able to keep track of your current games as well as buy new ones, a friends list, and being able to find friends online to play games with. However, despite the integrated service, each individual game works in a different way, so the mechanics of starting or joining a game will be different depending on what you are playing.
For people who prefer to stay on their computer for online gaming, there are several ways to do so. The first is through individual games. If you go to a store and buy a computer game nowadays, chances are it has an online component that is easily accessible through the game's interface. Again, this will change from game to game, depending on who made it and what type of game it is.
Another option is a network such as Steam. Created by software developer Valve (of Half-Life and Counterstrike fame), the Steam interface is a way to keep track of your games and friends online. Through the network they sell games and let people join games quickly and easily. It tracks your friends list and lets you know who is online playing what game when, and oftentimes lets you join them easily as well.
For a more immersive experience, you can try an MMORPG. To laymen that's a Massively Multiplayer Online Role Playing Game. The easiest way to describe it is online Dungeons and Dragons, but it can also be much much more. The most commonly known game in this genre is World of Warcraft, however there are MMORPGs with many different themes, such as Star Wars, Lord of the Rings, Superheroes, Star Trek... the list goes on. Chances are you can find one that you enjoy, if you don't mind spending a lot of time developing a character through quests. The communities around these games are die hard and fanatical, and that can be a good thing when you need help finding an item.
The thing to really keep in mind when joining online gaming is that the publishers have no control over the people who play the game. Although a game is rated "E", that does not mean that the people playing are going to be kid-friendly. Typed messages and voice chat are not censored, so that foul-mouthed person on the other team will be spouting profanities through your screen. A quick Google search can come up with several lists of the stereotypes met online. The sad thing is that every single one of them is true. The good thing is that a many games provide controls to help parents or thin-skinned gamers keep such things out. You can mute the voice chat or block text chats. You can mute or block specific players, and you can sometimes find games where there are rules against foul language or obscenities and those people will be booted from the game. Other parental controls can prevent certain games or games with certain ratings from being played, or the ability to limit the amount of time on a console or game. These controls are usually easily accessed (and password protected) from an options menu.