It is believed that the whole idea of dressing up in costumes started in Europe.  

Hundreds of years ago, when winters were much tougher than they are now (except for a burning fireplace, there was not much heat; food was not as plentiful as it is today, and people were afraid of the dark), long, cold winters used to cause worry for most people.

On Halloween, people used to believe that the ghosts came back to the world of the living, and that they would encounter ghosts if they left their homes.

To avoid being recognized by these ghosts, people would wear masks when they left home at night time.  By wearing masks, they hoped that the ghosts would mistake them for other ghosts.

On Halloween, to keep ghosts away from their homes, people would place bowls of food outside their homes to keep the ghosts happy and to stop them from entering their homes.

Of course, today, people play up on these old superstitions.  Kids and adults dress up by wearing masks and costumes.  And, people give out Halloween treats at their homes, so that kids don't play tricks on their homes.

Happy Halloween!!