This distribution of Linux started life as the Red Hat Linux project and was at one time the most popular distribution. In 2003 is became Red Hat Enterprise Linux (RHEL). Its mainly focused on the business world, as such it typically requires the purchase of a license . In return they offer a support to their customers.
RHEL is required to release their source code. Previously this was most commonly done through the Community Enterprise Operating System (CentOS). However this project has changed direction. At this time, Rocky Linux is the likely the best option to learn or operate on the source code of RHEL.
- Red Hat Website
https://www.redhat.com/en - Red Hat Linux
https://www.redhat.com/en/technologies/linux-platforms/enterprise-linux - RHEL Learning Labs
https://www.redhat.com/en/technologies/linux-platforms/enterprise-linux/learn - RHEL Documentation
https://docs.redhat.com/en/documentation/red_hat_enterprise_linux