Beyond the fact that both receive energy from the sun, the two types of solar energy systems are completely different.
Solar hot water systems collect radiation from the sun to heat a food-grade glycol fluid inside collectors mounted on a roof. This heated fluid is circulated and exchanges heat into a holding tank. The holding tank feeds solar-heated water into your domestic hot water system.
Solar electric systems convert sunlight directly into electricity. This electrical energy is then converted to be compatible with your utility service. It is then interconnected to your existing electrical system to reduce the amount of electricity that you need to purchase from your utility.