Sending Official Transcripts

I just submitted my Common App and I saw a message saying to make sure to send in official transcripts. Is this just in reference to the transcripts counselors upload on the Common App or something that needs to be sent separately? I checked the USC website and it never really clarified whether they had to be mailed in or not.

It refers to the ones sent in by your school/counselor, but I assume you have to let them know them to send them to a particular school.