It also differs from traditional RPGs because it doesn't require dice, charts of information, or lengthy lists of rules.  It's very straightforward: each player plays the role of a character from the DC Comics Universe, by posting their conversations, thoughts, and actions. This is done in response to events in the plot, as well as in response to other characters.  In this respect, it could also be called a 'round robin', or collaborative storytelling.  But it remains tied to its traditional cousins through the use of a guiding hand:  the Game Master (GM).

The GM is the player who runs the game.  He or she comes up with storylines to challenge the players, plays the villains they encounter, and often plays supporting characters and 'non-player' characters.  His job is the most difficult, but it can also be the most rewarding.  In the best games, however, all involved are rewarded with the feeling of being a part of a great story; perhaps of bringing their team, city, or character 'to life'.

How do I get a character?  Characters belong to specific games.  In some instances, characters may be duplicated (e.g., Batman in JLA, Batman in Gotham City); but in any case, the character belongs to each game's respective Game Master (GM).  Most GMs post their player/character rosters and update them as needed.  To determine whether a character is available, check the game's roster posts, or contact the GM via e-mail.

One problem with character selection is that there is always a high demand for certain characters, but not much turnover with players (such as Batman and Superman, for example).  Sometimes it's best to apply for a lesser known character or a supporting cast member, in order to show the GMs what you're capable of.  Then, when your dream character becomes available, you'll be in a much better position to apply for them.