Physically, candy is characterized by the use of a significant amount of sugar or sugar substitutes. Unlike a cake or loaf of bread that would be shared among many people, candies are usually made in smaller pieces. However, the definition of candy also depends upon how people treat the food. Unlike sweet pastries served for a dessert course at the end of a meal, candies are normally eaten casually, often with the fingers, as a snack between meals. Each culture has its own ideas of what constitutes candy rather than dessert. The same food may be a candy in one culture and a dessert in another.

The word candy entered the English language from the Old French çucre candi ("sugar candy"). The French term probably has earlier roots in the Arabic qandi, Persian qand and Sanskrit khanda, all words for sugar.

Before sugar was readily available, candy was based on honey. Honey was used in Ancient China, the Middle East, Egypt, Greece and the Roman Empire to coat fruits and flowers to preserve them or to create forms of candy. Candy is still served in this form today, though now it is more typically seen as a type of garnish.

In ancient India, pieces of sugar were produced by boiling sugarcane juice in ancient India and consumed as khanda. Persian contact with India meant the westwards spread of sugarcane, which entered the Arab world and became a key component of the Arabic agricultural system. The spread vof Islam across the mediterranean and Arabic conquests in the Mediterranean brought sugarcane to Cyprus, Sicily, Malta and the Iberian peninsula.

Before the Industrial Revolution, candy was often considered a form of medicine, either used to calm the digestive system or cool a sore throat. In the Middle Ages candy appeared on the tables of only the most wealthy at first. At that time, it began as a combination of spices and sugar used as an aid to digestion. Banquet hosts typically served these types of 'candies' at banquets for their guests. One of these candies, sometimes called chamber spice, was made with cloves, ginger, aniseed, juniper berries, almonds and pine kernels dipped in melted sugar. The Middle English word candy began to be used in the late 13th century.

However, it was not until the Elizabethan period that sugarcane-derived sugar became cheap and sufficiently cheap for a confectioner to become a culinary profession. Previous to this candy was often considered a form of medicine, either used to calm the digestive system or cool a sore throat. In the Middle Ages candy appeared on the tables of only the most wealthy at first. At that time, it began as a combination of spices and sugar used as an aid to digestion. Banquet hosts typically served these types of 'candies' at banquets for their guests. One of these candies, sometimes called chamber spice, was made with cloves, ginger, aniseed, juniper berries, almonds and pine kernels dipped in melted sugar. Elizabethan Manus Christi seems to have evolved as a medicinal confection in the Middle ages, hence the rosewater with ambergris and ground pearls. Later, in Elizabethan times Manus Christi became sugar confections coated in gold leaf.

Sugar candies include hard candies, soft candies, caramels, marshmallows, toffee, and other candies whose principal ingredient is sugar. Commercially, sugar candies are often divided into groups according to the amount of sugar they contain and their chemical structure. Hard-boiled candies made by the vacuum cooking process include stick candy, lemon drops and horehound drops. Open-fire candy, like molasses toffee and cream toffee, is cooked in open kettles and then pulled. Pan work candies include nuts and other candies like jelly beans and sugar-coated almonds, made by coating with sugar in revolving copper kettles. Gum work candy is cooked in large kettles fashioned for melting and moulded, dried and sugared like gum drops. They are soaked for a time in sugar syrup to allow crystals to form.

Chocolate is sometimes treated as a separate branch of confectionery. In this model, chocolate candies like chocolate candy bars and chocolate truffles are included. Hot chocolate or other cocoa-based drinks are excluded, as is candy made from white chocolate. When chocolate is treated as a separate branch, it also includes confections whose classification is otherwise difficult, being neither exactly candies nor exactly baked goods, like chocolate-dipped foods, tarts with chocolate shells, and chocolate-coated biscuits.