Pulse Width Modulation (PWM) is a method to create analog-like signal from the microcontroller digital output. It will achieve that by fast toggling of the pin with different ratio of logic HIGH and LOW. This ratio is called duty cycle.
This PWM signal can be used to set brightness when connected to some low power LED. With a proper power driver you can drive lots of power LEDs and LED strips. You can have up to 9 separate PWM channels.
bc_servo library you can connect a servo to the digital output and set the servo motor angle. You can use up to 9 servo motors.