What are the main differences between gta story mode and gta online?

The evidence describes Grand Theft Auto: San Andreas as a 2004 action-adventure game set in 1992 within the fictional state of San Andreas. It follows protagonist Carl 'CJ' Johnson's return home after his mother's murder, focusing on rebuilding his gang while confronting corrupt authorities and rival criminals. The game is played from a third-person perspective in an open-world environment where players navigate on foot or by vehicle. However, the provided evidence contains no information about GTA Online or its features, modes, or differences from story mode. Without verified data about GTA Online, any comparison would require speculation or external knowledge not grounded in the provided sources.