In some fantasy stories, an orc is a fictional creature that is often portrayed as a large, strong, and sometimes scary humanoid. It's kind of like a monster or a bad guy that you might see in movies or read about in books.
Now, slang is like a special way people talk that is different from regular words and phrases you might learn in school or from your parents. Sometimes people create slang words to sound cool or to fit in with a certain group of people. Orc, in slang, is a word that people might use to describe someone who is not very nice or friendly.
Imagine you have a playground at school, and there's one kid who always wants to push people and take their toys. You might call this kid an "orc" because they are behaving in a mean and not friendly way. It's like saying they are acting like one of those scary creatures from the fantasy stories.
But remember, it's not a nice thing to call someone an orc or any other mean name. It's important to treat others with kindness and respect, even if they are not always nice to us.