Linux Kernel is common to all Linux distributions and available to everyone as Open-Source software.

If you're new to Linux, you don't want to download the kernel, which is just a working Linux system component.

Instead, you want what is called a distribution of Linux, which is a complete Linux system.

There are numerous distributions available for download on the Internet and purchase from various vendors; some are general-purpose, and some are optimized for specific uses.

There are several guides for kernel developers and users. These guides can be rendered in several formats, like HTML and PDF. Please read Documentation > admin-guide > README.rst or online here.