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

The evidence available confirms Grand Theft Auto: San Andreas as a 2004 action-adventure game developed by Rockstar North, set in 1992 within the fictional state of San Andreas. The game follows CJ Johnson's return home after his mother's murder, featuring third-person perspective gameplay with open-world exploration on foot or by vehicle. However, the evidence contains no information about GTA Online, story mode, or any comparison between them. Without verified information about these modes, I cannot provide accurate differences between them.