Chord voicings.

A chord is defined as three or more notes played together while an arpeggio is defined as the notes of a chord played one at a time.  While some players and instructors will call a two note dyad a chord we will stick to the triad as our basic standard of harmony.

The three notes of the chord can be (and when strumming on guitar often are) duplicated.  The arrangement and number of duplicates of these notes can change.  As long as the root note is the lowest note sounded (the root is "in the bass") the chord symbol does not change and you are said to be playing an alternate voicing of the same chord.  To put it another way a chord voicing is another way of "spelling" or arranging the notes of the chord.   At first we just learn one or two convenient chord voicings for most chords and we play them on the first three frets of our instrument but this will change as we learn more and want to improve our chordal vocabulary.  This broadens our sound and can be one of the ways we express ourselves harmonically.

Here is Wikipedia on the subject:

Voicing (music)

From Wikipedia, the free encyclopedia

Various voicings: V/V-V-I progression.  1st (help·info),^[1] 2nd (info),^[2] 3rd (info),^[3] 4th (info), 5th (info)^[4] and 6th (info)^[5]

In music composition and arranging, a voicing is the instrumentation and vertical spacing and ordering of the pitches in a chord (which notes are on the top or in the middle, which ones are doubled, which octave each is in, and which instruments or voices perform each).
Voicing is "the manner in which one distributes, or spaces, notes and chords among the various instruments" and spacing or "simultaneous vertical placement of notes in relation to each other."^[6]
For example, the following three chords are root-position C major triads voiced differently:

Close position  Play (help·info)

Open position  Play (help·info)

Open position, doubled fifth  Play (help·info)

All three voicings above are in root position, while the first is in close position, the most compact voicing, and the second and third are in open position, which includes wider spacing. In triadic chords, close root position voicing is the most compact voicing in thirds which has the root in the bass. Open and closed harmony are harmony and harmonization constructed from open and close position chords, respectively.