I'm not sure as I haven't read it specifically. But generally, it might be about memories of past Christmases, perhaps featuring characters reflecting on traditions, family times, or special events that happened during previous Christmas seasons.
The main events include the calmness in the house as everyone is asleep. The stockings are hung waiting for Santa. Santa getting his sleigh ready with his reindeer. And his journey to deliver presents to children all over the world.
The night before Christmas, all through the house not a creature was stirring, not even a mouse. The stockings were hung by the chimney with care, in hopes that St. Nicholas soon would be there. It's a magical time when children are asleep, dreaming of the presents that might be left for them. Santa Claus is preparing his sleigh filled with toys, ready to make his rounds to all the good little boys and girls around the world.
The two most important characters are Jack Skellington and Santa Claus. Jack is the main character who drives the story forward. He's the one who discovers Christmas Town and tries to take over Christmas. Santa Claus is also key as he is the rightful figure associated with Christmas. Jack's actions affect Santa, like when he kidnaps him. There are also other characters like Jack's minions in Halloween Town who play a role in trying to execute Jack's Christmas plan.
The main plot is about Jack Skellington, from Halloween Town, who stumbles upon Christmas Town. He becomes fascinated with Christmas and decides to take over the holiday, but things go awry as his spooky Halloween ways don't quite mesh with the cheer of Christmas.
In 'the night before christmas short story', the main plot often revolves around the events on the night before Christmas. Usually, it includes the anticipation of Christmas, perhaps the activities in a household like children being excited and going to bed early in hopes of Santa's visit.
There are the children in the family. They are full of excitement and anticipation for Christmas. Then there's Santa Claus, who is on his magical journey to bring presents. The parents might also be considered characters, as they are part of the family scene, setting up the house for Christmas. There could also be the reindeer that pull Santa's sleigh, though they are more in the background of the story.