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

The verified evidence describes Grand Theft Auto: San Andreas as a 2004 action-adventure game played from a third-person perspective with open-world exploration on foot or by vehicle within the fictional state of San Andreas. The evidence specifically details the story mode, following protagonist Carl 'CJ' Johnson as he returns home after his mother's murder and works to rebuild his gang while uncovering truths about her death. However, the provided source contains no information about GTA Online, its multiplayer features, or any gameplay differences between the story mode and online components. Without evidence about GTA Online's mechanics, features, or structure, a comparison cannot be accurately produced.