This is a simple villager breeder. Two villagers, one of whom needs to be a Farmer, go in the area planted with potatoes. They will continually mate in order to try to meet to population capacity of the doors below.
A T Flipflop will toggle its output value whenever its input receives a positive signal, from a Button, for instance. The green Wool is T, the input. And the red Wool is Q and not Q, the outputs.