Kernel

graph TD
S["Software"]
K["Kernel"]
H["HARDWARE"]

S <--> K
K <--> H

Kernel operates hardware on low level

Whenever you compile and run your C code, then the C-library uses system calls

It accepts system calls to perform functions

Kernel is monolithic

more built in to it compared to other kernels (Windows NT, MacOS)
a lot of included drivers
GPU
peripherals (pen tablets)
don't get option to edit/remove features (unless you compile the kernel yourself)