What is a closed loop condensate system?

If I understand what you are asking, you are describing a steam cycle system.

First water is pressurized and pumped via a condensate pump (the water is called condensate. This condensate normally goes through a heater to increase efficiency, then is further pressurized by feed pumps. The water (now called Feed Water) is then sent through a control valve and into a steam generator (basically a large tea kettle). The control valve maintains constant water level in the generator within a certain range. The water in the generator is heated by various ways (Oil, Coal, Nuclear, Geothermal or even Solar reflectors). The steam produced is directed to do whatever work the system is designed to do, either heating, electricity generation, propulsion (steam locomotive / Steam powered ship). Once the steam has been used to produce work, it is at a lower temperature and pressure than it was in the generator. This low pressure steam can be directed to the condensate heater (as described above) then to a condenser, or straight to the condenser. The condenser uses various ways to further cool the steam; (water, cooling towers ;those big towers at nuclear power plants) and the resulting condensate is collected to be reused. The reason why it is called a closed loop system is that the water is re-used time and again in a loop. The water is only added to make up for leaks in the system (thus it is called make up water).