A loop is any passage set to repeat end to end without a gap, whether a two-bar drum pattern, a chord sequence or a sampled phrase. The idea predates computers. In 1948 Pierre Schaeffer noticed a damaged record repeating the same passage, a locked groove that he went on to use in musique concrète, and composers of the early 1950s spliced magnetic tape into closed loops. Hip hop pioneers later looped drum breaks by hand on turntables.
In jazz lo-fi, a loop is often just four or eight bars of chords played over and over while small details change around it. The repetition is deliberate: the music settles into a predictable cycle designed to sit in the background rather than demand attention.