Chocolate syrup

Chocolate syrup is a sweet, chocolate-flavored condiment. It is often used as a topping or dessert sauce for various desserts, such as ice cream, or mixed with milk to make chocolate milk or blended with milk and ice cream to make a chocolate milkshake. Chocolate syrup is sold in a variety of consistencies, ranging from a thin liquid that can be drizzled from a bottle to a thick sauce that needs to be spooned onto the dessert item. 
Chocolate syrup is also used to top puddings and cakes. Some restaurants use an artistic drizzling of chocolate syrup to decorate servings of cheesecake or cake, along with other decorations such as cocoa powder, powdered sugar or chocolate shavings. Some brands of chocolate syrup are marketed as chocolate milk syrup (e.g., Nesquik). Other brands are marketed as ice cream sundae toppings.
Ingredients.
A simple chocolate syrup can be made from unsweetened cocoa powder, a sweetener such as sugar, and water. Recipes may also include other ingredients, such as corn syrup, malt, and flavorings like vanilla extract.
Industrial recipes may contain ingredients such as:
Other uses.
Chocolate syrup was often used in black-and-white movies to simulate blood, because it was safe for the performers to swallow, easy to get out of clothing, and cheap to buy. It is also useful on black and white film for realistic viscocity. It was used in many movies, including "The Wasp Woman" and "Psycho".
Beginning in the 1890s, chocolate syrup was also marketed as a treatment for ailments, including for infants suffering from colic. In part due to the passage of the 1906 Pure Food and Drug Act, which required clear and accurate labeling, chocolate syrup began to transition from primarily medical application to commercial use.