Pulse Width Modulation (PWM) is a technique for getting analog results with digital means. Digital control is used to create a square wave, a signal switched between ON and OFF. If you repeat this on/off pattern fast enough with a LED for example, the result is as if the signal is a steady voltage between 0 and VCC controlling the brightness of the LED.
A servo motor is a type of motor that is designed to provide precise control of position and speed. It is a rotary actuator that can rotate to a specified angle with a high degree of accuracy. Servo motors are commonly used in a wide variety of applications, including robotics, factory automation, camera stabilization systems, and remote-controlled vehicles, to name a few.