Mikulás (or Szent Miklós) is the Hungarian version of Saint Nicholas, and a similar figure to Santa Claus. In many cities, Mikulás is getting more conflated with Santa Claus. Still, it is believed that Mikulás arrives to celebrate his day, December 6 (while some countries celebrate it December 5), and leaves before Christmas. This tradition is also well known in Romania (Moș Nicolae), Slovenia (Miklavž), the Czech Republic, Slovakia (both Mikuláš), Croatia (Sv. Nikola) and Poland (Mikołaj).
Although the role of gift-giver on Christmas Day itself is assigned to the Christ Child, on the eve of Saint Nicholas' feast day of 6 December, Hungarian children traditionally place a boot on their windowsill  waiting for Mikulás to come by and fill it with treats.
There is no Mrs. Mikulás in Hungary. In the Czech Republic, Slovenia and Slovakia, Mikulás/Miklavž often comes with two assistants: a good Angel who gives out presents to good children and a “Krampusz”, a mean elf, in some version a Devil, who punishes bad children.
On 6 December, they come to the houses where small children live and give them some presents. While "good" children receive various fruits, candies and toys, "bad" children can expect nothing more than a wooden spoon, several pieces of coal or carrot or potatoes left by Krampusz. (However, as no one is either all good or all bad, most children get both sweets and a switch.)
To earn some extra money, students often act as Mikuláš, the Angel, and the Devil. Treats are traditionally sweets, chocolate, candy and different nuts. In modern times, chocolate Santa figures are most common. To get the presents, the boots must be polished, because Mikulás does not fill boots that are not shiny enough.
Bad kids may also get onions, raw potatoes or a lump of coal in their boots next to their presents, as a warning that next year they might get only these.
Although presents are usually given to children by parents, it is not uncommon between adults to place small surprises (such as presents or a bunch of twigs) into the boots of others.