Power Consumption Basics
For our project we will typically have constant voltage sources that mostly deliver a constant potential difference. The power consumption of the device is its voltage multiplied by how much current it draws. Since we have a mostly constant voltage we can re-word that to be Power=V2/R. In other words the higher the resistance, the slower the electrons flow through a device and the less power it consumes. Transistors work a little bit differently since by design they ideally never have a current flowing from Vcc to ground. Their power consumption is due to the properties of the materials they are made of and the frequency they are working at. Most actuators work a little bit differently as well because they are usually controlled by turning the voltage on and off at a certain rate called a duty cycle.
Power drawn by transistors no matter what due to leakage current (power flowing through insulated material) and standby current (unintentional current between Vcc and ground). This draw can be minimized by design but during operation it just kinda happens unless if you unplug the device.
Power drawn by transistors due to them having capacitance and charging and discharging power during logic level changes. This is the majority of the power draw and is related to the frequency of the device (higher frequency quicker switches, more power draw in IC).
So for a lot of electrical devices such as motors, pulse width modifiers, etc the way they control the power (speed of motor) is by regulating how long the voltage is on and off for. The ratio of how long the device is on for versus the total operational period is called the duty cycle aka the power cycle and is typically represented as a percentage. A higher duty cycle means a higher power usage.
If your voltage drops below the minimum required for the mircocontroller to operate what happens is that there isn't enough of a potential difference for the logic gates to be operational. The problem is that you can get a state called brownout where some of the gates are operational and some aren't which would lead to super unpredictable operations. A lot of mircocontrollers have built in watchdogs for brownout detection that cause it to reset if it dips below the minimum voltage.