From RWP Wiki
Content Download is the process of downloading free or premium game content to your Xbox or Xbox 360's hard drive for use in a game. The most common types of downloadable content are levels, vehicles, and character skins. Downloadable content is usually created by the game's developer, although games with map editors - such as Free Radical Design's TimeSplitters: Future Perfect - may let you share and play on a custom map with other players. Because the developer is often responsible for creating downloadable content, downloadable content is usually not free when it is first released, although it may become free several months later. On the Xbox, players could charge the cost of downloadable content to the credit card used for their Xbox Live account. On the Xbox 360, players must use Microsoft Points to pay for downloadable content, although users can buy Points with a credit card and then use them on the Xbox Live Marketplace.
Kameo: Elements of Power was the first Rare game supporting Content Download that had content released for it. In late 2005, users could download a skin pack called the Winter Warrior Pack, which changed Kameo and the Elemental Warriors to look like holiday figures: Kameo donned a red Santa outfit and Ash donned a red, Rudolph-like nose, to use two examples. It originally cost 200 Microsoft Points, although it can now be downloaded for free. In 2006, two more skin packs - the Fright Warrior Pack and the Kameo Masquerade Pack - were released. The former changes the playable characters to resemble Halloween- or horror-themed objects, such as a skeleton and crawling eye, and the latter changes Kameo to resemble past Rare characters such as Joanna Dark. Both cost 200 Microsoft Points. A co-operative mode patch is also available for free, allowing two players to play through the action stages over System Link or Xbox Live.
On June 7, 2006, Rare released four new Perfect Dark Zero maps for download on the Xbox Live Marketplace: Gasplant, Trench, Plaza, and Rooftops. The "Perfect Dark Zero Map Pack One" costs 500 Microsoft Points and includes the Small, Base 1, and Base 2 sections of each of the four maps. On November 1, 2006, Facility and Ruin became available on the Xbox Live Marketplace for Gold-level subscribers. Major Nelson referred to them as "Map Pack Two," which brings up the question of what happened to Bases 3 and 4 of the original four expansion maps.