One will often encounter Roman numerals when reading a song transcription. Usually, at the beginning of a song, the chords, along with the key, and the tempo will be displayed. In some instances, the chord fingering and position will be exhibited and a Roman numeral may accompany a chord. The Roman numeral (such as B VII), means a B Major Chord is to be played on the seventh fret of the low E string, rather than in the first position of the second fret of the A string.
In position chords are those that occur in a “natural” position on the fretboard. For instance, an F♯ Major is played on the second fret, with the bass note on the low E string (2-4-4-3-2-2). Even if the base note is displaced to the D string (x-x-4-3-2-2), the chord is still in its most “natural” position, and contains all of the relevant intervals.