There have been a number of Italian soccer players that have worn the shirt number 8 both professionally and non professionally. There have been 6 soccer professional players with the number 8 on their shirt in the last year alone.
The number 10 is worn by the striker and usually the best player.
A player with the number 6 is usually a defensive midfilder. However, the number can be worn by any player.
Harry Kewell he plays for Australia (also known as the socceroos)
The number 84 is not a particularly common shirt number. No player who is particularly famous has ever worn it.