cool story bro:

In the Netherlands, Saint Nicholas' Eve (5 December) is the primary occasion for gift-giving, when his reputed birthday is celebrated.

In the days leading up to 5 December, young children put their shoes in front of the chimneys and sing 'Sinterklaas' songs. Often they put a carrot or some hay in the shoes, as a gift to St. Nicholas' horse. The next morning they will find a small present in their shoes, ranging from sweets to marbles or some other small toy. On the evening of 5 December, Sinterklaas brings presents to every child who has behaved him- or herself in the past year.
This is often done by placing a bag filled with presents outside the house or living room, after which a neighbour or parent bangs the door or window, pretending to be Sinterklaas' assistant. Another option is to hire or ask someone to dress up as Sinterklaas and deliver the presents personally. Sinterklaas wears a bishop's robes including a red cape and mitre and is assisted by many mischievous helpers with black faces and colourful Moorish dress, dating back two centuries. These helpers are called 'Zwarte Pieten' ("Black Petes")
The myth is, if a child had been naughty, the Zwarte Pieten put all the naughty children in sacks, and Sinterklaas took them to Spain (it is believed that Sinterklaas comes from Spain, where he returns after 5 December). Therefore, many Sinterklaas songs still allude to a watching Zwarte Piet and a judging Sinterklaas.