A pod is a receptacle where synthetically created humans are inserted and hardwired into becoming part of the power plant and virtually integrated the Matrix.
Humans are grown in the Fetus fields and, based on Morpheus' description of pods, are immediately connected by myriad umbilicals that not only provide the body with sustenance, but draw heat energy from the body to power the Machines and their city. They are gathered and transferred from by Harvesters to full pods in the power plant.
Central to the control of a human in the pod is a data probe that is firmly and permanently attached to the headjack, which provides connectivity of the human's mind into the Matrix. Each human pod can be compared to a radio station; a carrier signal for each human mind transmits and receives data from the Source to process information needed to form the neural-interactive world of the Matrix. Millions and millions of these pods are connected to cylindrical towers that form the power plant.
