Same-origin policy

The same-origin policy is a rule that says that websites are only allowed to talk to websites that are from the same place. Imagine that your house is the same place as your school - the same-origin policy is like a rule that says you can only talk to people from your house and your school. If you wanted to talk to someone from, say, the library down the street, you wouldn't be able to because the library isn't in the same "place" as your house and school. The same-origin policy helps keep websites and computers safe.