File Share
From Halopedia, the Halo wiki
A File Share is an online storage space for Halo 3 players. Every player gets their own File Share (one per Xbox Live gamertag) and may upload screenshots, films, film clips, map variants, and game variants.
By default, a File Share can hold up to six custom content items; players who subscribe to Bungie Pro (at the cost of 750 Microsoft points) will have their File Shares expanded to hold twenty-four items. For a limited time, Bungie Pro was free for four months with the purchase of the Legendary Map Pack.
File Share items are also displayed on Bungie.net. From Bungie.net, they can be organized into groups (called "File Sets") or downloaded to a computer.