Q: What does "Activation required" means??

I have an iPad one ... I tried to update it to the latest version, but when I turned it on a message comes up it says "Activation Required" I don't know what does this means

I tried to restore it via iTones, and when the setup page comes after the restoring process on the iPad another message pops up and it says "Your iPad could not be activated because the activation server is temporarily unavailable. Try connecting your iPad to iTunes to activate it, or try again in a couple of minutes. If this problem presists, contact Apple Support at apple.com/support"

I can't do anything with now ,,PLZ HELP ME