Can you tell me the meaning of the apple above my avatar?



Good question. Maybe it means you may be the next Isaac Newton?

I like Ernie’s answer, but the Avatar FAQ says, “The Activity Apple shows how active you have been on the site in the last 30 days. In addition, the Activity Leader in each language will receive a laurel wreath and the overall leader will receive a gold crown. There are 8 different levels to show your activity, all based on your Activity Score: …”

For more, see Avatar Help