Gate connected to the word line. When memory is to be read or written, the word line is activated.
Sensing circuits are connected to the bit line. And if the voltage in the capacitor is below a certain threshold then the data is read and the capacitor is fully discharged.
If the voltage is above the threshold then, the capacitor is fully recharged to (to represent the logic value 1).
So reading a value, essentially refreshes the capacitor's contents.
The source and drain are connected to the bit line and a capacitor (order depends on the type of implementation.
When the transistor is turned on, memory may be written in the form of a specific voltage into the capacitor. After the transistor is turned off, the capacitor will discharge and the memory might be lost.
Cons
Data has to be refreshed every few ms to avoid losing it.