choosing the right sensor

I need a sensor that detects if the user is moving or not ?

Do you mean a motion sensor?

You could just use a PIR motion sensor, which is commonly used for Arduino projects. Do you have something specific in mind?

to clear things up
I want to attach sensor on human body ,if he moves a code will happen

Tilt switch ?

Who is the lucky victim ?

An IMU like the MPU6050?