bootloader and USB Board and Mac

Sorry David but i've read the page about bootloader (one time in english and a second time with the stupid google translation to be sure to understand and i do).

Nowhere in the page it explain that this bootloader is in the microchip when you bougth a board :-/

it just explain that bootloader is needed and it explain how to put it in a serial board :o
therefore i ask !

regards

eric