A PTR record is a domain name pointer, i.e., it is used to point from an IP address to a domain or hostname. This is used for reverse DNS lookups. These records, used only with IN-ADDR.ARPA zones, should contain the canonical hostname of the machine referred to in the Canonical Hostname field.
⚠️ Usually the administrator of an IP address/subnet (i.e., your ISP or hoster) creates these for you (or gives you a web interface where you can configure this yourself), so you can ignore this feature.
