Confused about "thisBoardsSerialUSB" (respond ASAP due tomorrow)

I am working my way through this lighthack project for class and in the test sketch and the box 1 sketch it includes "thisBoardsSerialUSB" in the includes section. I am very confused by what this means. Do i leave it as "thisBoardsSerialUSB" in the code or do i change it to something? If i change it, what do i change it too??