What is this...

[looper]

stuff? I am reading about this flasher thingy. Can you d/l roms off the internet or can you acquire these on a disc and then upload them to the card or how does this thing work. I have read the faqs, but I am not really sure what this 'flasher' does. So if you could answer these I would greatly appreciate it. I have seen GBA roms for different gaming consoles, are you able to use these with this?