What does "scanning" mean, in this context? Scan by a local antivirus? Scan by a local AI model that alerts the user to possible legal issues? Scan by a local government-mandated black-box model that blocks/censors messages? Scan and send suspicious messages to the police for further investigation?

I think it's related to https://github.com/element-hq/matrix-content-scanner-python, but that page also assumes the reader already knows what "scanning" means.