HiDon’t worry, we all were in your shoes when we started (no idea what all these abbrevations meant!)
ITA (Invitation to Apply) is when CIC invites you to apply for Permanent Residency based on the information (and docs) you provided for calculating the score.
After that, we will need to provide more documents (such as Police Certificates, full travel & address history, etc) and apply for Permanent Residency. This is what CIC calls a complete application package.
Once the application is submitted, CIC will send a confirmation that they have received your application. This is called AOR (Acknowledgement of Receipt). Most of the timelines are calculated from when you get AOR, i.e when CIC has officially received your application.
How long does it take CIC to send Medical request after AOR?