He has an English language link to his blog here and Spanish here.
Wiki says, "The cuatro of Venezuela has four single nylon strings, tuned (A4,D5,F#5,B4). It is similar in shape and tuning to the ukulele, but their character and playing technique are vastly different. It is tuned in a similar fashion to the traditional D tuning of the ukulele, but the A and B are an octave lower. Consequently, the same fingering can be used to shape the chords, but it produces a different inversion of each chord."
"The cuatro is the national instrument of Puerto Rico. It belongs to the lute family of chordophones (or string instruments). However, very little is known about the exact origin of the Puerto Rican cuatro. Most experts believe that the cuatro has existed on the island in one form or another for about 400 years.
The Spanish instrument that it is most closely related to is the vihuela poblana (also known as the Medieval/Renaissance guitar), which had 4 courses, 2 strings each for 8 strings in total as well as the Spanish Medieval/Renaissance 4 course and the Spanish Laúd, the last of which is still found in the Canary Islands".
What a beautiful latin sound. Those high inner strings really ring.