Just looked it up. It's sort on like early Christmas apparently.
Sinterklaas is the original Santa Claus. Dutch settlers brought the tradition to America, where it transformed into Santa Claus. We celebrate Sinterklaas on december 5th, giving presents to eachother, similar to Christmas in other countries. It was recently in the news as the UN deems the tradition to be racist, because Sinterklaas is helped by a black man, zwarte piet. They think this has it's roots in the slavery history. Which is utterly ridiculous as the tradition f zwarte piet is formed hundreds after slavery was banned here, it's just a children's event.