RDWC stands for Recirculating Deep Water Culture, an advanced version of Deep Water Culture (DWC).
The recirculating aspect ensures even dispersal of nutrients and water throughout the system, and can also help to keep temperatures stable, which is an important condition for healthy plant growth.
In a DWC system, plants have their roots suspended in a nutrient and oxygen-rich water solution. In a RDWC system, the solution gets recirculated, rather than remaining static,
The main benefit of RDWC is that all of the plants are connected in one large system, so all of the maintenance can be done from a single point, rather than on every individual bucket in a DWC system.