RHEL (Red Hat Enterprise Linux), CentOS and Fedora are popular Linux distributions (distros). While they are all based on the same source code and share many similarities, there are some key differences between them:

1. Support: RHEL is a commercial product that comes with paid support from Red Hat. CentOS is a community-driven project that is provided for free without official support. Fedora is a community-driven project that receives limited support from Red Hat.

2. Release cycle: RHEL releases are very slow and occur every 2, 3, or 5 years depending on the version. CentOS releases follow RHEL releases with a delay of a few months. Fedora releases are frequent, usually every 6 months.

3. Stability vs. bleeding edge: RHEL and CentOS prioritize stability and security over introducing new features. Fedora, on the other hand, is aimed at providing the latest and greatest software.

4. Packages: RHEL has a limited set of packages compared to Fedora and CentOS. CentOS contains almost all the packages that RHEL has, plus some additional packages. Fedora has the largest package repository of the three, with more experimental packages and cutting-edge software.

5. Purpose: RHEL is generally used for enterprise-level production environments. CentOS is often used as a free and open-source alternative to RHEL, particularly for testing and development. Fedora is often used by enthusiasts and early adopters who want to try the latest features and software.

In summary, RHEL is a commercial product with long-term support and stability focus, CentOS is a community-driven alternative to RHEL that offers similar stability features, and Fedora is a community-driven distribution that provides a bleeding edge platform for testing new features and technologies.