The packaging helper utilities provide a small amount of tooling that is similar to Debian's dpkg toolset, but for the BSDs, where the packaging systems are FreeBSD's pkgng and NetBSD's pkgin.
If you are familiar with Debian's dpkg, where a package source tree has a debian/ top-level subdirectory with a debian/rules file plus various staging areas, the rules file invokes commands like dpkg-gencontrol, and the process is controllable over all with a dpkg-buildpackage command; then the packaging helper utilities enable a similar kind of system.
A package source tree has a bsd/ top-level subdirectory with a bsd/rules file and bsd/tmp plus other staging areas, which can be processed with a pkg-gencontrol utility invoked by that rules file, and the entire process controllable with a pkg-buildpackage command.
FreeBSD pkgng and NetBSD pkgin are not as complicated as Debian's dpkg, and the tasks of the helper utilities can be achieved with shell script.
However, they provide a degree of usage consistency across platforms, and are also more efficient.
In particular, pkg-gencontrol when it was developed replaced an existing shell script system that forked two entirely new processes, to run the sha256 and the BSD stat commands, for each file to be processed (including hard‐linked duplicates), with an in‐process hash calculation and the simple printing in octal of the file permission bits.
This, plus checks to ensure that the same file contents via different hard links were not hashed multiple times, did indeed turn out to be observably faster at creating package manifests.