The primary use of suet is to make tallow in a process called rendering, which involves melting and extended simmering, followed by straining, cooling and usually a repetition of the entire process.
Unlike suet, tallow can be stored for extended periods without refrigeration. It is used to make soap, for cooking, as a bird food, and was once used for making candles.
The type sold in supermarkets is dehydrated suet.
Suet recipes