noob question

[IFR]

Hello
i have few questions about PS2
what is the difference between NTSC and PAL ?
if i have a ntsc ps2 can i play pal games ?
what does a patch for ps2 games ? to bypass a game protection when you make a backup ?
Also I would like to buy a ps2 and i was wondering which version is the most convenient to install modchip in order to play backup games ?

thanks for the answers