PPR = Passport request, if you hold a mainland passport you will get a email to submit your passport to get COPR which is landing paper.
For HK and Taiwan passport holders, in the recent cases Hong Kong visa office sends COPR directly to your mailing address, few cases still get the PPR letter, but the big differences is they can submit the copies of passport instead, the mainlanders have to submit the physical passports only.
For more information you may find the answers in this link https://docs.google.com/spreadsheets/d/1FAYZyQgud1lzp7fM28i2O8ZrfbMAxdTc_t7_fiwI6ak/edit#gid=1493682450