"Mark 11" is a chapter from a book called the Bible. It's a very important book for many people because it helps them learn about God and how to live a good life.
In this chapter, a man named Jesus is riding on a donkey and people are cheering for him and putting down their cloaks so that the donkey doesn't have to walk on the ground. They are treating him like a king or a important person.
Jesus goes to a temple (a special building where people go to worship God) and he sees people selling things and making money inside. He gets very upset because he thinks they are using God's house for the wrong reasons. So he gets rid of all the people and animals who were selling things and tells them that the temple is a place for prayer and not for buying and selling.
Later in the chapter, Jesus and his disciples see a fig tree and Jesus is hungry. But when they go to get figs from the tree, there are no figs on it. Jesus gets angry and tells the tree that it will never bear fruit again. The disciples are confused, but Jesus is trying to teach them a lesson about faith and being fruitful.
So, in summary, Mark 11 is a chapter from the Bible about Jesus going to a temple and getting rid of people who were using it for the wrong reasons, and also about Jesus teaching his disciples an important lesson about faith and being fruitful.