gif
Short for graphic interface format. A file format in which a graphic is rasterised and stored in bitmap form, usually for reproduction at low resolution (typically 74 dpi) on a computer screen. Gifs are rarely of a high enough resolution to print well.
Greyscale
Method of representing continuous tone images on a monitor or printer
gsm
Abbreviation of grammes per square metre. The usual method of indicating the substance of paper or board on the basis of weight.