Figured bass is also called thoroughbass or basso continuo.
“The composer wrote out only the melody and the bass. The bass was played on one or more continuo instruments—for example, harpsichord, organ, or lute—usually reinforced by a sustaining instrument such as a bass viola da gamba, violoncello, or bassoon. Above the bass notes, the keyboard or lute player filled in the required chords, which were not otherwise written out. If these chords were other than common triads in root posiiton, or if chord tones (such as suspensions) or accidentals beyond those in the key signature were required, the composer added numbers (figures) or signs above or below the bass notes.”
From Donald J. Grout and Claude V. Palisca, A History of Western Music, Fifth ed. (New York: Norton, 1996).