HW/SW Interface

What exactly does hardware/software interface mean? I was looking at a job application that says I should have understanding of it, but I've never seen that phrase before.

imagine you have a piece of code in C or machine language that offers symbols that other code can jump to, but also uses the hardware IO ports to do some operation with hardware or manages memory structures, maybe outside user mode

it basically means being familiar with C and assembly, reading datasheets and manufacturers manuals, but yeah with better context better answers would come