The traditional purpose of cheesecloth was to wrap cheese in, as the name in English implies.
It is a cotton cloth made in a loose weave. There are fine and coarse versions, though when the weave gets very fine, the line between cheesecloth and butter muslin starts to blur. You can get it bleached and unbleached .
Cheesecloth doesn’t shed lint, doesn’t lose its strength when wet, and doesn’t impart any flavour to food.
It can be used for straining, as a pouch for putting a bouquet garni in, lining moulds, or wrapping delicate foods such as fish in before poaching. In book binding, cheesecloth is sometimes used as a fabric to line the spine of the book.
It is usually sold in bags at stores. You can also buy it by the yard in fabric stores, if you use a lot of it. You can cut larger pieces into smaller pieces as needed.
It can be washed and reused several times.