The American-Arab Anti-Discrimination Committee is a group of people who work to make sure that everyone who is from an Arab background is treated fairly and equally in the United States. They want to make sure that people aren't discriminated against because of their cultural or religious background.
Imagine you went to school and nobody wanted to play with you or be your friend because you looked different than everyone else. That would make you sad and frustrated, right? The American-Arab Anti-Discrimination Committee tries to stop that from happening to people who come from Arab backgrounds by talking to people in power (like the government) and telling them that it's important to treat everyone fairly, no matter where they come from.