What are Bases

[madpa]

Now look we were all newbies from the start but i just dont understand bases. I know theyre the first 6 digit cards to tell what type of card they have but i dont understand stuff like World_W18(World MIX). How do u read this as so that you know what its talking about or even something like US_KNIV(USA). Im not sure how to read this and im gonna need help with this one so please and ty