A ski lodge is a game first created by T.O.N. where players go on a trip or vacation of some sort and eventually everyone gets killed except one person, who is the (randomly selected) murderer. They don't all have to take place at a ski lodge, they're just typically called that because the first few by T.O.N. did happen at a ski lodge. 

The people who are entering usually pack a few things and bring their assorted AEs and CAPTCHAs, and then the story commences. The person who started the thread will tell the story through parts - or "days" - and sometimes will require CBer contributions, such as journal entries or cooking competitions or something else along those lines where the CBers will make personal decisions that affect the story.

Every day, the murderer, who is randomly selected at the start of the adventure, kills someone in a variety of unpleasant ways. The person who dies every day is also usually randomly chosen, whether by dice or pulling names out of a hat / sugar bowl. There is usually a lot of filler and/or plot twists every day, which builds up to the "conclusion" at the end of every day where someone dies.

Different stories are run different ways, but usually the murderer is not revealed until he or she kills everyone else in the story, and then it ends, although it is worth noting that unfortunately, most ski lodges are abandoned or forgotten before they ever reach the end. If you ever consider writing one, try not to let that happen, because it can be very annoying for the people who participated *cough*Abigail S*cough*

Hope I explained that alright. Any other questions?