In American English, "fries" are "French fries", deep fried potatoes usually cut into strips, like you find at McDonalds and other restaurants. "chips" or "potato chips" are thinly sliced potatoes that come in a bag. You can usually find these in grocery stores and vending machines.
In British English, they say "chips" instead of "fries", and "crisps" instead of "chips".
In both dialects, fries and chips (or chips and crisps) are thought of as completely different things, even though they are both made from potatoes.