Technically, there is no such call as "handball" in soccer, and yet this is an area where a lot of confusion arises.  Law 12 of the game states that one of the penal offenses (fouls) is "handles the ball deliberately".  No matter how hard you look, you will see no reference in the law to "Hands", to "Handball", or even to "gaining an advantage" by handling the ball, although that is often the appeal that gets made.

It's pretty straightforward actually - if it is deliberate, it is a foul.  Anything else and play should continue.

"But it was in the penalty area" is another argument often heard from coaches and parents, but it still doesn't matter (unless it is deliberate of course). 

So how do referees know if it is deliberate, without being mind readers?  One guide they use – did it look like "ball to hand" or "hand to ball"? The latter is the one that needs to be called.

Still, not all deliberate handballs are deliberate. No, that's not a typo.  If a ball is blasted towards a player's middle bits, and that player deliberately moves his hand to deflect what will likely be a very painful impact, experienced referees will not penalize the player for doing so.  A similar situation would be when players in a "defensive wall" protect their heads from being knocked off.  If the action is done in self defense, it should most often be ignored.  It would also be incorrect to penalize players when an opponent has blasted the ball towards them from close range and, with no time to react, the ball makes contact with the hand.

The real question that needs to be asked is why are so many "handballs" called that apparently should not be? One reason is that inexperienced referees find this is an easy call to make, one that most people demand, and one that few people will argue with.  Referees who call the play correctly, however, can often be heard to say "no intent, keep playing", and that is the key - if there was no intent on the part of the player to handle the ball deliberately, players should just keep playing.
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