It means they're currently logged in to Chess.com. Which in turns means they may make their own move quite quickly, as the next time they do something that refreshes their screen, they will get the message that it is their turn to move.
The Little Green Square

does the green square with a capitol F in the middle mean unrated and if so how can I get the rating

does the green square with a capitol F in the middle mean unrated and if so how can I get the rating
That's your avatar. I believe that is a default one based on creating your account with Google.
You play rated games by creating your game challenges as rated, which it looks like you have been doing.

thanks , Question abuot rating inbalance. I often able to win agaist computer on 13oo level but get beaten by live opponents that has
way lower level than I'm. how is that possible?

thanks , Question abuot rating inbalance. I often able to win agaist computer on 13oo level but get beaten by live opponents that has
way lower level than I'm. how is that possible?
Because bot ratings are often wildly inaccurate.
Games with computers used to be rated here but that was stopped several years ago because some people were using the lower rated bots to build up their ratings. (This is called "farming".)
What does the little green square in the lower portion of your opponent's avatar mean when playing daily chess?