These two fields allow to specify a different default assignee for ticket opened against this package in bugzilla. Note: The EPEL field is always displayed for packages in the 'rpms' namespace regardless of whether it is used in bugzilla or not.
The systemd-extras package provides optional systemd components as sub-packages, such as systemd-networkd and systemd-timesyncd, which are not part of Red Hat Enterprise Linux 8 (and possibly derivates).