* Crisps: These are thin, potato-based snacks that are fried or baked and come in a variety of flavors. Think of them like potato chips in American English.
* Chips: These are thick-cut, deep-fried potatoes, typically served as a side dish with meals, often fish and chips. They are similar to french fries in American English.
So, if you ask for "crisps" in a British shop, you'll get a bag of potato chips. If you ask for "chips" in a British restaurant, you'll get a portion of french fries.