Scientific Linux (SL) is a distribution of the Linux operating system, which was created jointly by Fermilab and CERN, with the support of various laboratories and universities from around the world. It is made from source code for versions of Red Hat Enterprise Linux under the terms of the end user license agreement.
Recently, more and more people have been switching from using Scientific Linux to Red Hat's CentOS. And finally, Fermilab announced that Scientific Linux 8 will no longer exist, and they will pour all their developments into CentOS.
Source: linux.org.ru