Traditionally sausages were made out of the natural casing. The natural casing was the cleaned intestine or stomachs in olden times used to give the meat the shape and typical size.
However, the casing has now been replaced by collagen or cellulose. There are even plastic casings available for the purpose. To know more about chicken sausage via https://hellers.co.nz/products/sausages.
Sausages are obtained from ground pork which is seasoned with herbs and spices and then pressed into the casing for the shape. It is a popular belief that sausages came from Italy; however, the truth to that belief is yet to be found. Sausages are classified into different categories depending on their consistency and preparation method.
You have the cooked sausages that are completely cooked and leave nothing raw while being served. They require refrigeration is one does not plan on eating them right away.
The next type is the sausage that is derived by smoke cooking. Pork meat is susceptible to worms and one may find ringworms in under-cooked pork. Hence it is extremely important to thoroughly cook the sausage. Smoke cooking is an excellent method of cooking and is the safest because it leaves no chance for ringworms. Smokes pork can be eaten cold or hot. They are generally packaged and sold at later times.
Freshly smoked sausage is also available. These are, as the name suggests, served and consumed right after they have been smoked, hence they retain the freshness and are very tasty!
You also have cured and fermented and dried sausages. These are kept for a longer time and do not spoil easily, they are eaten cold as an accompaniment.