PIR sensors (or passive infrared sensors) are motion sensors that measure subtle changes in infrared light in the room and register that change as movement. The processing is done on the chip and it outputs a current based on whether or not it detects motion.

int pin = 2;

void setup(){
  pinMode(pin, INPUT);

  pinMode(13, OUTPUT);
}

void loop(){
  int pirVal = digitalRead(pin);

  if (pirVal == 0) {
    digitalWrite(13, HIGH);
  } else {
    digitalWrite(13, LOW);
  }

  delay(100);
}

#include <Servo.h>

Servo myservo;  // create servo object to control a servo

// twelve servo objects can be created on most boards

int pos = 0;    // variable to store the servo position

void setup() {

  myservo.attach(11);  // attaches the servo on pin 9 to the servo object

  // initialize serial communication at 9600 bits per second:

  Serial.begin(9600);

}

void loop() {

  // read the input on analog pin 0:

  int sensorValue = analogRead(A0);

  //remap sensorValue from 0-1024 to 0-255

  pos = map(sensorValue, 0, 1024, 0, 179);

  // tell servo to go to position in variable 'pos'

  myservo.write(pos);

  // print the value of variable "pos"

  Serial.println(pos);

}