The three access levels include Free, Premium and Legendary accounts, each of which offer varying levels of access to game content. According to the press release:
Free Access: New players now have access to the base game content in DC Universe Online, including Gotham City, Metropolis, and all current raids and alerts outside of DLC packs. Free Access provides players with the ability to create two characters, join a League and many other benefits. Free level players can also purchase DLC packs, additional character slots, and more in-game.
Premium Access: Any player who has spent at least $5 USD (including former paid subscribers and new players who have purchased $5 of in-game items) qualifies for the Premium Access level. Premium level players have more benefits available to them than the Free level player, including additional character slots, additional inventory slots, and higher cash limits. DLC packs, additional character slots, and more can be purchased in-game. All previous subscribers are granted Premium Access automatically.
Legendary Access: Legendary Access provides the most content, features and benefits of the three access levels. Loaded with enhanced features, Legendary Access is available for a $14.99 USD monthly fee (multi-month discounts are available) and includes access to all DLC packs at no cost, more than 16 character slots, over 60 inventory slots, the ability to form Leagues, and many other benefits.
Let us know if you'll be checking out DC Universe Online, now that it's free to play.