Expressing surprise, disbelief or incredulity.
Expressing that the speaker can continue speaking without interruption from the listener.
Expressing encouragement, see come on.
To proceed.
To use and adopt (information) in order to understand an issue, make a decision, etc.
To happen (occur).
To continue an action.
To continue in extent.
I think I've said enough now; I'm not sure I should go on.
To talk about a subject frequently or at great length.
Well, typically used to express exasperation, a matter-of-fact or unenthusiastic attitude, or helpless acceptance of something surprising.