Arduino is all about electronic, and electronic refers to electricity. This may be your first dive into this amazing universe, made of wires and voltages, including blinking LEDs and signals. I'm defining several very useful notions in this part; you can consider turning down the corner of this page and to come back as often as you need.
Here, I'm using the usual analogy of water. Basically, wires are pipes and water is electricity itself.
Voltage is a potential difference. Basically, this difference is created and maintained by a generator. This value is expressed in Volt units (the symbol is V).
The direct analogy with hydraulic systems compare the voltage to the difference of pressure of water in two points of a pipe. ...