A Nutrient Film Technique (N.F.T.) is exactly what the name implies.
It is a thin film of solution that flows along the bottom of the channel, thus watering the plants which are in small net pots inset along the channel.
These pots sit lightly touching the base, or just above the base of the channel and the media within them acts like a wick drawing the moisture and nutrients up to the plant roots.
A small pump like those used in fish tanks, is placed in the reservoir which holds the nutrient solution, from here it is pumped up to the channels which are positioned in such a way the flow of solution can carry through from one channel to another. The slight angle the channels are placed on, assist in the continual flow eventually returning to the reservoir tank.