MaximumYield explains Kratky Method:
The Kratky method is a simple system that would be well-suited to gardeners experimenting with hydroponics. This method of hydroponics works in a similar method to deep water culture systems, but it does not require as much equipment or materials. In the Kratky method, plants are placed in a net pot with a growing medium and then placed into a reservoir. The reservoir is then filled with conditioned water and a nutrient solution until the mix covers the bottom of the net pot. As the plant grows, it will absorb water while simultaneously growing roots into water. Then, as the water level declines, plant roots will be exposed to much-needed oxygen.
Check out Jeb Gardener’s explanation:
This guy’s channel is entertaining and filled with interesting hydroponics experiments.