The cruyff turn is performed by dribbling, for example with the right foot, more or less towards the defender, to the side of the defender. Once you get closer to the defender, the left foot lands right next to the ball with the toe pointing 90 degrees to the side. The inside of the foot is facing towards the opposite player. After you plant that foot, the body weight totally shifts to the left foot, while the right foot comes around the ball and taps it with the inside of the foot. Also, the toe is pointing 90 degrees to the side, so you're almost sideways to your original position, passing the ball with the inside of the foot back to where you came from behind the supporting leg.
After this touch is performed, you turn around and go back the same way you came from. After that, you have many options, to continue to the opposite side of the field, or to keep dribbling, or pass the ball towards the goal or back to your defenders. That's the basic idea of the cruyff turn.