A mat is a border of matboard used to enhance and protect artwork. Appropriate presentation of artwork with mat and frame makes the artwork more attractive and appealing, thus creating a more saleable product. Most shows and galleries require pieces to be matted and framed.
Humidity has a lifelong effect on paper, causing it to expand and contract.
If paper comes in contact with sufficient moisture, tide lines or even mold may develop. If paper becomes too dry, eventually the fibers may become brittle and if handled carelessly, may crack and break. Matting and framing provide a shield to protect artwork when handling. Artwork may be damaged by condensation forming on the inside of the frame's glass. This moisture is a result of temperature changes.