Vellum was originally a translucent or opaque material produced from calfskin that had been soaked, limed and unhaired, and then dried at normal temperature under tension, usually on a wooden device called a stretching frame. Today, however, vellum is generally defined as a material made from calfskin, sheepskin, or virtually any other skin obtained from a relatively small animal, e.g., antelope. Some authorities do not even distinguish between vellum and parchment, although traditionally the former was made from an unsplit calfskin, and consequently had a grain pattern on one side (unless removed by scraping). while the latter was produced from the flesh split of a sheepskin, and consequently had no grain pattern. The important distinction between vellum (or parchment) and leather is that the former is not tanned but is prepared essentially by soaking the skin in lime and drying it under tension.

Most medieval manuscripts, whether illuminated or not, were written on vellum. Uterine vellum was made in the 13th and 14th centuries from the skins of unborn or still-born animals.

Limp vellum or limp-parchment bindings were used frequently in the 16th and 17th centuries, and were sometimes gilt but were also often not embellished. In later centuries vellum has been more commonly used like leather, that is, as the covering for stiff board bindings. Vellum can be stained virtually any color but seldom is, as a great part of its beauty and appeal rests in its faint grain and hair markings, as well as its warmth and simplicity.