How Does A Boost Converter Work?
A boost converter works in two stages, ON and OFF. In the ON stage the Semi-conductive Switch is conducting and current builds up in the inductor producing an electromagnetic field, this field stores energy. In the OFF stage the Semi-conductive Switch does not conduct and the electromagnetic field collapses. When the field collapses the energy stored in it can not escape through the Semi-conductive Switch so it goes through the diode and into the load/Capacitor at a much higher voltage. This happens several thousand times a second via the pulses from the NE555 Timer Chip and the result is being able to charge a high voltage capacitor from a low voltage source.
Below is some aid for those of you who do not know electronics well.
VR-Variable Resistor (also called a Potentiometer)
U / IC-Integrated Circuit
Q-Transistor / IGBT
GND-Ground (Negative terminal of Battery for Portable Applications)
Some Diagrams and Charts are shown below to help you further.