GNU/Linux Debian Installing Linux Kernel Headers Guide
Hi! The Tutorial shows you Step-by-Step How-to Install Linux Kernel Headers in Debian GNU/Linux Distribution.
And the Debian Kernel Headers contain the C Header Files for the Linux Kernel.
Which offers the various Function and Structure Definitions required when Compiling any Code that Interfaces with the Kernel, such as Kernel Modules or Device Drivers and some User Programs.
Last, possibly to Install a Custom Kernel with Headers you may see: Installing Kernels Tutorial.