When I read through the differences between Cent, OpenSuse, and Fedora, they frequently say that Cent and Red Hat are binary compatible. My experience has been (debian/ubuntu) that regardless of distro binary files will run and packages are compatible if they use the same package manager. So why do these articles emphasize that Cent and Red Hat are binary compatible or are my assumptions wrong.
Building on @John Siu's answer the terminology is confusing if you're not familiar with the Redhat technologies.
New technology usually shows up first in Fedora where it is worked out. Fedora distros usually have a shelf life of 6 months. At any time 2 releases are being actively supported, after which updating for it is dropped.
Once technologies have been proven out in Fedora they'll eventually show up in a release of RHEL. RHEL's shelf life is 10 years of production followed by 3 years of extended coverage. See here for full details.
CentOS is another community project that isn't sponsored by Redhat but does have their blessing. CentOS provides the same identical packages as RHEL with the RHEL branding stripped out and/or replaced with CentOS logos and branding. CentOS is sponsored by several customers that have very large numbers of computers but don't want to have to pay for a subscription of RHEL for each box. The CentOS project doesn't offer any support other than staying in lock step with updates as they come out for RHEL.
There are a lot of other distros that make use of
CentOS and RedHat are binary compatible because CentOS is RedHat without the RedHat logo.
Quote from CentOS own FAQ
In About CentOS, the ftp sources are listed