ESC/POS is a set of printer-control commands introduced by Epson for use in point of sale (POS) systems. It differs from the ESC/P commands used on many Epson printers, primarily the dot-matrix variety. Most commands are "escape sequences" consisting of the ESC character followed by various other characters, but some of the other ASCII C0 controls are also used.
Commands can do things such as set different character sets, fonts, and formatting, as well as printing bar codes. The specific supported features vary between printer models. The command set appears to be smaller and simpler than that of ESC/P, and includes commands specifically geared to POS systems such as one to open the cash drawer.