Asealis a device for making an impression in wax, clay, paper, or some other medium, including an embossment on paper, and is also the impression thus made. The original purpose was to authenticate a document, a wrapper for one such as a modern envelope, or the cover of a container or package holding valuables or other objects. The sealing process is essentially that of a mould, with the final image represented on the device for making the impression by a mirror-image design, incised in sunken- (or counter-) relief or intaglio. Recently, a new kind of seal appeared: seal tags which normally come with hang tags. This kind of seals are loved by most of enterprises from garment or clothing industry, toys or accessories industry and some other relative industry.

Seals were used in the earliest civilizations and are of considerable interest in archaeology. In ancient Mesopotamiaseals were engraved cylinderswhich could be rolled from one side to another to create an impression on clay, sometimes used as a label on a consignment of trade goods. From Ancient Egyptseals in the form of signet-rings of kings have been found. Recently, seals have come to light in South Arabiadatable to the Himyarite age. One example shows a name written in Aramaic(Yitsḥaq bar Ḥanina) engraved in reverse so as to be visible in the impression. In the Indus Valley Civilization, rectangular seals were used to label trade goods, these seals played the same part as the common seal tags in the market.

Because seals are commissioned by individuals and carved by artists, every seal is unique, and engravers often personalize the seals that they create. The materials of seals and the styles of the engraving are typically matched to the personalities of the owners. For example, design of seal tags for different brands are always different from each other.