The earlier loose association known as the Fives Forum, with the full support of both the Rugby Fives Association and Eton Fives Association Boards became known as the Fives Federation on 7th February 2005.
Eton Fives is a handball game, that is hand & ball, nothing to do with 'five-a-side' football, or any other games, and it is played on a special court in a similar way to Squash. Fives comes in several flavours, and various styles, but they all have the one significant thing in common, you hit the ball with your hand, not a racquet, bat, paddle or anything else, usually wearing gloves, because the balls are hard.
The fundamentals of the game are to hit the ball against a wall, within a defined playing area, and to continue to return it within one bounce in such a way that your opponents can't do the same. If you ever hit a ball against a wall with friends at school you will get the general idea!
In the UK there are three major variations of the game, and this site is for Eton Fives which is the most interesting variation. There is a full description of the game and it's origins on the About menu.