Mirin refers to a Japanese sweet alcohol made from mochigome and komekoji (yeast). It is generally used only for cooking, but it is also used as a ceremonial drink, called otoso at New Years. There are two types of mirin: hon and shin. Shin mirin has less than 1\% alcohol content.
Mirin enhances flavor and makes food shiny and its sweetness is essential in cooking Japanese dishes and sauces.