The article describes the process of package pinning in Ubuntu
Example:
cat /etc/apt/preferences.d/mirantis_openstack
Package: *
Pin: release l=pike
Pin-Priority: 1100
Package: *
Pin: release l=pike
Pin-Priority: 1100
mirantis_openstack is the name of an entry in list of repos:
cat /etc/apt/sources.list.d/mirantis_openstack.list
deb [arch=amd64] http://apt.mirantis.com/xenial/openstack/pike nightly main
deb [arch=amd64] http://apt.mirantis.com/xenial/openstack/pike nightly main
l=<label> it is the label of the repository. Many repositories have empty labels
o=<origin> this tells about the origin of the repository. Official Ubuntu repository has
Ubuntu as the valuev=<version> is the version of a distribution. It's 16.04 for Xenial
a=<suite> is same as Archive. From debian wiki it's is The name of the distribution of Debian the packages in this directory belong to (or are designed for), i.e. stable, testing or unstable.. For Ubuntu, these are
release-updates, release-security etc. For example, xenial-updates, xenial-security. It's shown in the output as a=xenialc=<component> tells about the licencing thing. It's main, multiverse, restricted, universe in Ubuntu. In the output it's shown as c=main or c=restricted etc. Most PPAs use main for this field
b=<architecture> is about the OS architecture. Shown as b=i386 or b=amd64 in the output
n=<codename> is the release name of the distribution. For 16.04 it is xenial. For 14.04 it is trusty. Shown in apt-cache policy output as n=xenial or n=trusty