For PCCs, you need one from your country of origin, if you lived there for >6 months after turning 18. You also need a PCC from any country you lived in for >6 months after turning 18.
For Canada, you don't need to provide one unless they specifically ask you to. But many people (including myself) did provide it as it is where we 'currently live' and I've been here >6 months. For a Canadian PCC, you need the RCMP Criminal Background Check (
http://www.rcmp-grc.gc.ca/en/steps-obtain-certified-criminal-record-or-vulnerable-sector-vs-check) basically. You have to go to an RCMP-accredited fingerprinting center (
http://www.rcmp-grc.gc.ca/en/who-can-conduct-criminal-record-check#ac) where they take your fingerprints and submit them electronically to RCMP to run through their database. In a week or so you receive the PCC paper in the mail. Use this tool to find out how to get a police certificate for any country:
http://www.cic.gc.ca/english/information/security/police-cert/index.asp
If you select Canada in the tool, it will explain this to you. IRCC only accepts the RCMP's criminal record check for PCC, not local police station police certificates.