LED: Standard 5mm Red LED
Forward voltage: ~2.0V
Current: ~20mA typical (but works fine a bit lower)
Resistor: 220Ξ©
Keeps current around:
(5Vβ2V)/220Ξ©β13.6mA(5V - 2V) / 220Ξ© β 13.6mA(5Vβ2V)/220Ξ©β13.6mA
Bright enough, but also very safe for the Arduino pin (max is 40mA per pin, recommended β€20mA)