What is exactly distortion on my amp?

I am new in guitar and amp , so i have no idea what is it. As i know , my amp has 6 type of sound effect which is blues , overdrive, crunches , clic , super lead and heavy metal. Therefore , i dont know whether distortion is belongs to those effect or it covers everything. If distortion is 1 type of effect , how can i set to my effect to distortion? Please guide me. Thanks