CentOS (Community ENTerprise Operating System) is a Linux distribution based on and compatible with Red Hat’s commercial Red Hat Enterprise Linux. Each CentOS version is supported for 10 years. Each version is updated every 6 months to support new hardware.
Red Hat Enterprise Linux is free and open source software but is available as binary discs for paid subscribers only. As required by the GPL and others, Red Hat provides all source code. The CentOS developers use this source code to create a final product that is very close to Red Hat Enterprise Linux and available for download. There are other clones of Red Hat Enterprise Linux based on this code.
CentOS uses the yum program (starting with version 7.0 the dnf package manager is used) to download and install updates from the CentOS Mirror Network repository, while Red Hat Enterprise Linux gets updates from Red Hat Network servers. CentOS up to version 5.0 also used the up2date program for updates.
Among other things, CentOS was used as the default OS in the Cluster Compute Instance (CCI) project from Amazon, the essence of which is that the capacity of a large number of standard rack servers is leased.
Based on materials wikipedia…