An alphabet font, (also referred to as a digitized font, or pre-digitized font) is not really a font, it is a style of letter designs that are in the stitch file format (PES, XXX, etc.) and you wil have a folder that contains separate files for each letter (eg A.pes, B.pes). Each of these files are stitch files, or embroidery designs, so they have limited capabilities – you cant resize these designs, or skew or change them much, because they are stitch files. An ESA font is an actual font that you can load into your computer once, and use as a keyboard font. ESA fonts are professionally digitized for embroidery. It is easier to type on the keyboard with an ESA font than bring in each letter separately.