Portuguese guitar

The Portuguese guitar is a plucked string instrument with twelve steel strings, strung in six courses comprising two strings each. It has a distinctive tuning mechanism. It is most notably associated with fado, although it has and is being used in a broader context.
Portuguese guitar Models
There are two distinct kinds of modern Portuguese guitar models : the Lisboa guitar and the Coimbra guitar.
The differences between the two guitars are their scale, body measurements and other finer construction details. Overall, the Coimbra guitar is of simpler construction than the Lisboa guitar.

Visually and most distinctively, the Lisboa guitar can be differentiated from the Coimbra guitar for its larger soundboard and scroll ornament above the tuning machine in place of Coimbra's teardrop shaped motif. The Lisboa guitar has a narrower neck, smaller string spacing and a slightly shorter scale.
Both guitars have a very distinct timbre - the Lisboa guitar has a resonant bell-like sound that the Coimbra guitar lacks; the Coimbra guitar has a more accentuated bass sound.

Technique
The technique employed to play the Portuguese guitar is what is historically called dedillo or dedilho. This technique comprises playing solely with the thumb and the index fingers. On the Portuguese guitar the strings are picked with the corner of the fingernails, avoiding contact of the flesh with the strings. The unused fingers of the picking hand rest below the strings, on the soundboard. Nowadays most players use synthetic materials in place of natural fingernails; these fingerpicks are usually made of plastic or tortoiseshell.