Corn starch is starch derived from the corn of (maize) grain. The starch is obtained from the endosperm of the corn kernel. Corn starch us a popular food ingredient used in the thickening of sauces and soups, and is used in making corn syrup and other sugars.
Corn starch is used a a thickening agent in liquid-based foods (e.g., soup, sauces, gravies, custard, usually by mixing it with a lower temperature liquid to form a paste of slurry. It is sometimes preferred over flour alone because it forms a translucent mixture, rather than opaque. As the starch is heated, the molecular chains unravel, allowing them to collide with other starch chains to form a mesh, thickening liquid.
Corn starch is also a main ingredient in bath bomb fizzies.