The fuse panel inside the vehicle is usually for the headlights and electrical accessories such as the heater, radio, power windows, seats, defroster, etc., while the one under the hood (which is sometimes called the "power distribution center") is for high amp systems such as the ignition circuit, fuel injectors, starter motor, fuel pump and antilock brake system
Most domestic cars built up until the late 1980s had only the one fuse panel inside the vehicle. The other high amperage electrical circuits were typically protected by "fusible links," special pieces of wire that were designed to melt just like a fuse if the circuit was overloaded.
The Japanese and Europeans started using a separate fuse panel under the hood for the engine-related circuits almost a decade before the domestic automakers primarily because most of these vehicles were fuel injected. As fuel injection became more common on domestic-built cars, the need for a second fuse panel became obvious and fusible links were soon replaced with fuses.
The fuses under the hood are typically large capacity fuses (30 amps or more) while those inside a vehicle are typically 20 amps or less.