Hello Tizianos,
A variable can only have one value at a time. This is a value from 0 through 255. All integer values in this range can be stored. (0, 1, 2, ..., 253, 254, 255) If some task needs a percentage this value will be converted to a percentage automatically.
The variable can be used to fade 1 channel from 0% to 100%. (0%, 1%, 2%, ..., 98%, 99%, 100%) You can use this variable for multiple things. The thing I described in the example is controlling a channel. However you can do other things as well.
The IoCore has 8 variables. Which allows you to control 8 channels in this way. In you setup every GPI pin would use 1 variable. To control a total of 8 channels with a fade.
Best regards,
Guido