Thank you so muchECAS - Electronic Client Application Status... I’m assuming the E is for electronic because the site just says Client Application Status. Basically this site for checking your application status: https://services3.cic.gc.ca/ecas/security.do?app=ecas&lang=en
AOR - Acknowledgment of Receipt: a formal acknowledgment, usually email (most common format these days), from the IRCC that they’ve received your application and have probably begun processing it too. Usually an application will sit in the mailroom for a while, so once it’s been picked out you get your AoR