It is the time in seconds after which the metadata will expire.

But you can create and use a local repository to install packages and dependencies. If you do not have an RHEL subscription, you cannot use the default online repositories to download and install packages. While learning and testing, you need to install several packages and dependencies. That is perfectly fine if you want to use RHEL for testing or learning in the LAB environment. But it also means that you will not get updates and support from Red Hat. It means you can download and use it without purchasing a subscription. RedHat releases RHEL Linux under the GPL license. A subscription not only allows you to download the latest and updated packages but also allows you to get technical support from Red Hat.

If you want to use an RHEL system in the production environment, you should purchase it. To get it, you need to pay a subscription fee. If your system is registered with the RHN network and you have an active RHEL subscription, you do not need to do any additional configuration or setup to install RPM packages. But for this, you need to register the system to the RHN network and purchase an active RHEL subscription. When you install RHEL Linux, the installation process automatically configures the necessary settings the local system needs to connect and download any required package from these repositories. RHEL Linux uses online repositories to store and manage RPM packages.

Yum list repos