Simple syrup is a sugar syrup made from equal parts of sugar and water, cooked lightly into a syrup. There are many types of simple syrup, depending on the ratio of sugar to water and the type of sugar used. Rich simple is a 2:1 ratio of sugar to water.
Simple syrup is used to provide a neutral sweetness to cocktails, and ensures no grainy undissolved sugar in the finished drink. While there are commercial versions of this bar staple, most of them are full of preservatives and other chemicals, and it is easy to make. Making a batch, letting it cool, and adding about a quarter cup of vodka per cup of syrup to preserve it takes twenty minutes.
Simple syrup should be stored in the refrigerator, labeled with the type and date.