It's about Ice Hockey, Susan.
The 'Goon' is a term used for a player who is used aggressively for fighting the opposing team. Also called an Enforcer.
The film is okay. A comedy. A ice hockey player becomes the Goon due to his fighting skills. Spoilt for me by a character who seems to shout "F**k" every few seconds. I saw it at the cinema but if I never see it again I would not be bothered.
Stay in and watch
SLAPSHOT (1977) instead. A far more awesome film comedy about the same sport. You do not need to be an Ice Hockey fan to enjoy Slapshot either and is recommended.
I watch Ice Hockey by the way. Local team GUILDFORD FLAMES and I have a season ticket.