Explaination of dd command in nasm

I am reading osdev wiki. I came across these two lines of code.

 nasm kernel.asm -f开发者_如何学Go bin -o kernel.bin
    dd if=kernel.bin of=/dev/fd0

I can understand the first line but I can't understand the second line. what the second line do? what is this dd command? what is this /dev/fd0 here? Can anybody explain me this please? Thanks in advance.

dd is a utility that allows you to copy a file. The if parameter stands for 'input file' and of is output file. The command here is copying the kernel.bin onto the /dev/fd0 device.

It's just copying kernel.bin to a floppy disk (/dev/fd0).

$ man dd