This is what Cisco book says about PAC phases:
.....
Phase 0: The PAC is generated or provisioned and installed on the client
Phase 1: After they authenticate each other, they will negotiate a TLS tunnel
....
What will be installed on the client in phase 0? a certificate? they only refered as "PAC" I have read some other websites but they don't explicitly say if it is a certificate...
I would appreciate your help!
EDIT: After researching more I have found that it is not a certificate but some files, but what kind of files?:

I found this from CWSP-205 book