It suggests being a passive observer rather than an active participant. It's like being a spectator at a game, watching from the sidelines instead of playing.
Here are some examples of how it can be used:
* "I couldn't just sit on the sidelines while my friends were getting bullied." (Meaning: They chose to intervene instead of passively watching.)
* "She's been sitting on the sidelines of the political debate, waiting to see who emerges as the frontrunner." (Meaning: She hasn't taken a strong stance yet.)
* "I'm ready to get off the sidelines and make a difference." (Meaning: They're ready to become actively involved.)
The idiom often implies a sense of:
* Indifference: Not caring enough to get involved.
* Hesitation: Being unwilling or afraid to join in.
* Observation: Watching and learning before taking action.