Kaggle is a website on which users can submit statistical models/programs/predictions into competitions, often involving rewards and many competitors. The goal

Kaggle is a website on which users can submit statistical models/programs/predictions into competitions, often involving rewards and many competitors. The goal is usually to make interesting and insightful models based on a sample dataset. Overfitting occurs roughly when you tailor your model too specifically to the sample data. For instance, a regression with 10000 parameters might fit the data really well, but only because we included so many useless parameters. A poorly designed contest on Kaggle had a submission that deliberately overfit. If you're curious, there are many ways to address overfit models (look up model selection or AIC)