You may be wondering what it is with on and off, and how this translates into physical parameters or electrical signals. These will soon become clear.

We live in a world of analog signals-a countless number of colors that the eyes can see, a countless number of sounds we can hear, and a countless number of smells, and so on.

But with digital electronics, such as Arduino, we deal with discrete or distinct sets of values.

Logic levels, in a nutshell, describe the state that a signal is in. In digital electronics, such as Arduino, there are two logic states: 0 and 1. Since there are only two states, it is also called binary logic. This is also commonly translated to ON or HIGH for binary 1 and OFF or LOW for binary 0.

For Arduino, a HIGH signal is 5V, and LOW is 0V. This is how these logic levels manifest themselves physically in terms of voltage.

The Arduino uses these logic levels on its I/O pins to either take input from the outside world or give an output.

We shall see...