Our is a possessive determiner that shows something belongs to or connects with the speaker and at least one other person. When you say “our house,” you mean the house that belongs to you and your family. When your teacher says “our classroom,” she means the room shared by everyone in the class.

The word creates a sense of shared ownership or connection. Think about how different these sentences feel: “I need to clean my room” versus “We need to clean our room.” The first is just you. The second means you share the room with a sibling or roommate, so you share responsibility for it too.

Our can refer to small groups, like “our team” meaning your soccer team, or enormous groups, like “our planet” meaning Earth, which all humans share. Sometimes our creates a feeling of unity and belonging: when someone says “our school” or “our country,” they're emphasizing that everyone is part of the same community.

Notice that our always includes the speaker. If your friend is talking about her family's car, she'd say “our car,” but if you're talking about it, you'd say “their car” since you're not part of that family.