What does this mean? Well, from the Kernel Programming Guide,
Modules are pieces of code that can be loaded and unloaded into the kernel upon demand. They extend the functionality of the kernel without the need to reboot the system. For example, one type of module is the device driver, which allows the kernel to access hardware connected to the system.
Neat, eh? So basically, 'extend your operating system with Rust.'
I'm excited to see this flurry of ultra-low-level activity from the Rust community. I'm sure there's more neat stuff to come!