The numbers correspond with the diagram. Below is a definition of each compenent.
Radiator The radiator is the most prominent part of the system. Coolant that has traveled through the engine is pumped through the tubes of the radiator and is cooled off for another round.
Radiator Hoses Your cooling system has a number of rubber hoses that move the fluid from one place to the other. These need to be replaced before they become brittle and cracked.
Water Pump The water pump does what you think it does - pumps the coolant through the system. The pump is belt driven, except in the case of some race cars that use an electric water pump.
Thermostat Your engine isn't always the same temperature. When you start it on a cold morning, you want it to get warm quickly. If you stop in traffic, you want it to cool itself off. The thermostat controls the flow of coolant so that it cools down more or less depending on the temperature of the coolant. It rests in a housing just after the radiator bottom hose.
Electric Cooling Fan Many cars these days have an electric fan for either primary or added cooling. The fan draws air through the radiator when you aren't moving fast enough to get things cooled down.
Thermo Time Switch Also known as the fan switch, this is the temperature sensor that tells the electric fan when to blow.