Final answer:
The 'p' in ATmega328p refers to 'Pico-Power', which indicates the microcontroller's capability to operate with very low power consumption.
Step-by-step explanation:
In the context of the ATmega328p microcontroller, the letter 'p' refers to 'Pico-Power'. Pico-Power is a technology used by Atmel (now acquired by Microchip Technology) that allows microcontrollers like the ATmega328p to operate at extremely low power consumption, making them ideal for battery-operated devices where energy efficiency is crucial. This technology enables the device to utilize various sleep modes to significantly reduce power consumption when it's not performing active operations.