On facebook, what do the little circles in the chat box mean...?

[abc123...]

sometimes the circle is green and sometimes it is grey what do they mean because I have only joined facebook a week ago and I had the feeling th green meant the person is on facebook and the grey is when the person is not on facebook but is on the internet. Am I wrong???

 

[Goldfish]

no you are right, green is on, gray is off and a crescent moon means they are idle

 

[clashcityrocker!]

green is online, grey is idle

 

[Daisy]

green is that they are availbale and online

grey means they are logged on but idle, so havent done anything for a bit

 

[skwee]

Green means they're online.
Gray means they're idle.
Red means they're offline.

 

[skwee]

Green means they're online.
Gray means they're idle.
Red means they're offline.