The main differences are in the usage and in the design. Although they look similar, pots usually have 2 smaller handles, one on each side, while saucepans usually have one longer handle. The usage part differs because pots are used mostly to boil things like water or pasta or similar things inside, while a sauce pan is usually used for making sauces because reduction is much easier since you can move the saucepan as you see fit while you stir with the other hand.