Tallow is a rendered form of beef or mutton fat, processed from suet. It is solid at room temperature. Unlike suet, tallow can be stored for extended periods without the need for refrigeration to prevent decomposition, provided it is kept in an airtight container to prevent oxidation.
Rendered fat obtained from pigs is known as lard.
Industrially, tallow is not strictly defined as beef or mutton fat. In this context, tallow is animal fat that conforms to certain technical criteria, including its melting point, which is also known as titre. It is common for commercial tallow to contain fat derived from other animals, such as pigs or even from plant sources.