CBSA Notes refers to information related to your visa application or border crossing obtained from the Canada Border Services Agency.
Prior to the pandemic CBSA provided information via postal mail only. Currently CBSA follows the same protocol as IRCC and provides information via email as a PDF document.
Like IRCC, CBSA also uses the GCMS (Global Case Management System) software system. As a result, GCMS Notes and CBSA Notes look similar, with the exception, that in most CBSA Notes the security details are not redacted. CBSA Notes also contain all the information available about your file with CBSA including the travel history for entry/exit history in Canada.
The CSIS Notes on the other hand disclose when your file was received, and when the processing was completed, along with all the information CSIS has pertaining to your file. PR applicants can check the status of their security/background check with CSIS.