There is a System to get PR of Canada called Express Entry(EE) on the basis of your skills and work experience, and study etc. more likely you can say that it is a point system, and there are some categories under EE to apply... and Provincial Nomination Program (PNP) is one of them.... BCPNP EE (British Columbia Provincial Nomination Program - Express Entry ) is completely different from cic's EE. In BCPNP EE your file will accessed according to the rules and regulations set by BC's government to nominate an applicant for Federal PR. Once you have approval in BCPNP EE you will be awarded with 600 points in your cic's EE profile which you will make your points higher enough to get selected in next EE draw (Please NOTE ! that you will get 600 points only when you have applied BCPNP EE, and if you have applied under regular stream (paper file) you will not get 600 points means you cannot use your PNP to apply PR under EE in cic, you have to make a paper application to cic (As I know) ). Remember you must have an EE profile in Federal EE (cic's EE) and Job Seeker code before you apply for BCPNP (or for any PNP EE)....
So, PNP is a process in which a provincial government nominate you to Federal Government (by giving you a PNP Certificate) that he/she is eligible to live permanently in BC and in Canada (that he/she have permanent job, and he/she paying taxes properly etc.) and then Federal Govt will consider your application according to their rules and regulations in the present time when you submit your file to cic.
AOR stands for Acknowledgement of Receipt. That mean PNP office giving you an acknowledgement that they have received your file and it is complete.