Due to the length of the video we are not able to show the blinking of the LED gradually speeding up. 

A potentiometer is a variable resistor that varies the amount of resistance in the circuit based on the position of a dial or slider.  In this circuit the dial is used to control how fast the LED blinks. 

Manual tune and auto tune effect the brightness and sensitivity of the led and photo resistor. Manual tune allows the user to easily change the sesnsitivity of the photo resister and how dim the led starts hen it is lit up. Auto tune automatically controls the sensitivity of the photo resister and how bright the LED is. Manual tune is easier to control certain parameters of the code while autotune is easier to use and gives you less control over the circuit.