You are looking at a code browser for Linux.
By using this web interface, you can navigate the source code of Linux by following simple links, search it by using the box in the navigation bar, or use vi inspired key bindings to move within files.
It should all be pretty intuitive, but to get started, here are a few things you may want to try:
sbexr is free software (as in "free speech"), under heavy development. sbexr.rabexc.org and the Linux kernel source code are used as a playground to test new features, observe bugs, and gather feedback. Check there often if you want to see new features in action.