learn PARTS IN YOUR KITS need for arduino(part-3)

Optocoupler - This allows you to connect two circuits that do not share a common power supply. Internally there is a small LED that, when illuminated, causes a photoreceptor inside to close an internal switch. When you apply voltage to the + pin, the LED lights and the

internal switch closes. The two outputs replace a switch in the second circuit

Piezo - An electrical component that can be used to detect vibrations and create noises.

Photoresistor - (also called a photocell, or light dependent resistor). A variable resistor that changes its resistance based on the amount of light that falls on its face.

Male header pins :- These pins fit into female sockets, like those on a breadboard. They help make connecting things much easier.

Potentiometer :- A variable resistor with three pins. Two of the pins are connected to the ends of a fixed resistor. The middle pin, or wiper, moves across the resistor, dividing it into two halves. When the external sides of the potentiometer are connected to voltage and ground, 

the middle leg will give the diference in voltage as you turn the knob. Ofen referred to as a pot.