User blog comment:Zero-ELEC/No DRM in Brotherhood/@comment-3254365-20110224121429/@comment-1142365-20110224175243

DRM is the acronym for Digital Rights Management, which are certain protocols used to restrict the amount of access to the game (though gameplay is usually not affected by this unless you own a pirated or otherwise modified copy). Usually, it requires authentication from an online server, and therefore the internet is needed to play the game, in Assassin's Creed's case, the authentication would probably be through Uplay.