
I see nobody else has answered you.
I don't recall ever coming across a definition of orbs; but what people are talking about are spherical coloured lights (balls of energy) that have an existence here on the physical plane (as opposed to being "seen" or perceived only with energy self, they are seen with eyes). I have read about them being picked up by cameras before.
Psychics that see them feel that they are a representation of a living presence (higher spirits); as opposed to the phenomenon of "ball lightning" which seems to be an undirected, natural occurrence, although we don't understand what brings it about.
I have never seen orbs myself (though my daughter and her friend have, at least a couple of times). I told her not to be afraid, because they are the presence of benign spirit energies, guides. I see kind of dots of light, but it seems as if I am not seeing them on this plane, it seems like looking further than this plane ...
A friend of mine saw a ball of white light in her house, shortly after her uncle had died. She heard his voice speaking to her from it (no dire messages, just letting her know he was OK to ease her grief). I am not sure whether this would be called an orb in the usual sense that psychics describe them.
Sorry I can't give the sort of definitive information you have asked for!
All the best,
Tish