Miso is made from fermented soybeans.There are several types of miso. The most common is mugi miso, a combination of soy and barley with a warm, mellow flavour. Hatcho miso is made from soybeans alone and is denser and more strongly flavoured. Genmai miso which is made from rice is lighter and sweeter.
Miso is a living food in the same way that yogurt is and contains bacteria and enzymes which are destroyed by boiling. Miso is best added as a flavouring at the end of cooking.
Miso is a bit like peanut butter in texture and has a high salt content. The lighter coloured the miso the less salt.