Any game involving kicking a football. There are many games that are refered to as football, including
Soccer,
Rugby League,
rugby union,
touch rugby,
Australian Rules and
Grid Iron.
The specific rules for football differ depending on your whereabouts. Football is generally used to refer to the most popular game in a given region.
Remember this kids ..... Soccer, Rugby League, rugby union, touch rugby, Australian Rules and Grid Iron are all football.