From Wikipedia and also from my own memory which goes back beyond the 90s:
“Passer rating (also known as quarterback rating, QB rating, or passing efficiency in college football) is a measure of the performance of passers, primarily quarterbacks, in American football and Canadian football.[1] There are two formulae currently in use: one used by both the National Football League (NFL) and Canadian Football League (CFL), and the other used in NCAA football. Passer rating is calculated using a player's passing attempts, completions, yards, touchdowns, and interceptions. Since 1973, passer rating has been the official formula used by the NFL to determine its passing leader.[2] Passer rating in the NFL is on a scale from 0 to 158.3. Passing efficiency in college football is on a scale from −731.6 to 1261.6.”