A potentiometer is a simple knob that provides a variable resistance, which we can read into the Arduino board as an analog value. They can be attuned from zero ohms to whatever maximum resistance that is specific to it. For example, a potentiometer of 10 kΩ can be adjusted from 0 Ω to its maximum of 10 kΩ.
We often use the power supplies like batteries or direct AC/DC supply which are normally in higher ranges compared to the actual requirement for the circuit. In that cases we need this kind of voltage regulators which can regulate and vary the voltage levels for the circuit requirement.
The AMS1117 series of chips are linear voltage regulators with low voltage drop. The modules based on the AMS1117 chip provide constant 3.3V or 5V outputs from an unregulated DC input. It's very compact and can be included in your project schema or you can use it together with a breadboard for circuit testing.
Hibernation was designed for laptops and might not be available for all PCs. It uses less power than sleep and when you start up the PC again, you're back to where you left off. Hibernation suspends to disk unlike the sleep option that suspends to RAM. That's why it takes a bit longer to wake up from hibernation than from sleep.