confusion with kernel/OS

Hi. just very general questionS. From mini6410 manual,
i see that to run android in my board, I need kernel, bootloader and file
system. We dont need OS to run it in the board. Yeah, I did it and
android in my board works so well.
Then I guess Android OS = Android kernel + bootloader + file system
IS is right? IF it isn't, how can we run and see android in my board
without android OS?

Actually, what I wanted to do is that change some code from Android OS
source and build it, and install it into my 6410board.
The manual explain how to build ANDROID source code by typing
./build-android. Yeah, I did it and some files are created.(such as
system.img, ramdisk, .. etc) SO, WHAT IS THE NEXT STEP? HOW TO INSTALL THEM
INTO MY BOARD SO MY OWN CUSTOM ANDROID SOURCE CAN BE RUN IN THE BOARD?

Nobody helps me!

by the way, i want to use sd card to do this.
my computer dont have connection with serial port and
serial-usb converter does not work well