Lego Star Wars: The Complete Saga is a video game based on the Star Wars-themed toy line by the Lego Group. It is a combination of the game Lego Star Wars: The Video Game and its sequel Lego Star Wars II: The Original Trilogy.
The DS version does not have any online play. Also, the DS version does not include any new characters or levels, and several levels have been deleted, in addition to free play on vehicle levels, however it does include a few new mini games.
Source: Wikipedia, "Lego Star Wars: The Complete Saga", available under the CC-BY-SA License.
The Nintendo DS version makes use of adapted levels from the original LEGO Star Wars game, but is not a compilation title including all the features from that game.