This instrument is a Spanish guitar without frets, the reason why is called Arabic guitar and not Spanish fretless is because it was conceived with the idea of performing arabic music on it, or to be more specific, to play styles of music based on Maqams, like arabic, turkish, or others.

The construction of an Arabic guitar is that of the Spanish but doesn't include frets mounted on the fretboard, an easy way to enjoy this instrument is to take a Spanish guitar and just pull off the frets filling up the gaps left on the wood. Differences are to be found between Spanish and Arabic guitars, specially in the tunings which allow the player to perform the ornaments so characteristic of the style, these also help to perform the right and left hand techniques required to get the quarter tones as well as tremolos and other special effects usually found on Oud playing. Without these it would only sound like a simple fretless guitar still played western style.

The issue of the name is also important because of both the spiritual and mind state required to perform music, obviously it doesn't feel the same playing arabic music on a fretless guitar as it would be in a genuine Arabic guitar.