In typography, all caps (short for "all capitals") refers to text or a font in which all letters are capital letters, for example: "THIS TEXT IS IN ALL CAPS". All caps may be used for emphasis (for a word or phrase). Messages typed completely in capital letters are often equated on social media to shouting and other impolite or argumentative behaviors. This became a mainstream interpretation with the advent of networked computers, from the 1980s onward.

Source: Wikipedia