Video Terminal 220 - A text-mode terminal standard that defines special control sequences to control things on the terminal like character bolding, cursor position, reverse video, bell-ringing, etc. It also defines a set of control sequences for special keyboard keys, such as break, and F1-Fn function keys.

The standard is very similar to the ANSI X3.64 standard. In fact, X3.64 borrowed heavily from earlier Video Terminal (VT) standards.

Just like X3.64, VT-220 and other VT standards define special control sequences using a Control Sequence Introducer or CSI. The CSI is usually the two byte values: "Esc-[" (0x1b, 0x5b). It may also be a single byte code in 8-bit systems.

There are other VT standards as well. Earlier versions included vt-100, and later versions included vt-320. VT-220 was the most popular of the text based standards before GUI standards, such as X-Windows replaced them.