CentOS is a community-driven free software effort that provides two Linux distributions (CentOS Linux and CentOS Stream) and a variety of Special Interest Groups releasing packages to run on those distributions. CentOS Linux provides a free, community-supported computing platform functionally compatible with its upstream source, Red Hat Enterprise Linux (RHEL). CentOS Stream is a continuously delivered distribution that tracks just ahead of RHEL and acts as an upstream for RHEL development.

History
Prior to becoming known under its current name, CentOS originated as a build of CAOS Linux,which was started by Gregory Kurtzer.
In June 2006, David Parsley, the primary developer of Tao Linux (another RHEL clone), announced the retirement of Tao Linux and its rolling into CentOS development. Tao users migrated to the CentOS release via yum update.
In July 2009, it was reported in an open letter on the CentOS project web site that CentOS's founder, Lance Davis, had disappeared in 2008. Davis had ceased contribution to the project, but continued to hold the registration for the CentOS domain and PayPal account. In August 2009, the CentOS team reportedly made contact with Davis and obtained the centos.info and centos.org domains.
In July 2010, CentOS overtook Debian to become the most popular Linux distribution for web servers, with almost 30% of all Linux web servers using it. Debian retook the lead in January 2012.
In January 2014, Red Hat announced that it would sponsor the CentOS project, "helping to establish a platform well-suited to the needs of open source developers that integrate technologies in and around the operating system". As a result of these changes, ownership of CentOS trademarks was transferred to Red Hat, which now employs most of the CentOS head developers; however, they work as part of Red Hat's Open Source and Standards team, which operates separately from the Red Hat Enterprise Linux team. A new CentOS governing board was also established.
On December 8, 2020, a representative of the CentOS Governing Board, and Red Hat employee, announced that the CentOS community would be "shift(ing) focus" from traditional CentOS Linux, to CentOS Stream.Initial community response to this announcement was overwhelmingly negative. Soon thereafter, CentOS founder, Gregory Kurtzer announced a new project to continue the original CentOS focus, which became known as Rocky Linux. Similarly, Cloud Linux (makers of CloudLinux OS) announced a new CentOS clone named AlmaLinux.