Panels
Convert sunlight to DC electricity. Monocrystalline is more efficient; polycrystalline is cheaper.
Inverter
Converts DC to the AC your home uses. Hybrid inverters also manage a battery.
Battery
Stores power for night or outages. Lithium lasts longer; lead-acid is cheaper upfront.
Net meter, mounting, wiring, protection
The balance-of-system parts that make the whole thing safe and grid-connected.