The Venezuelan Cuatro is a particular instrument that has been used in this country and some other countries for decades. It’s so popular that there’s practically no genre inside the country that has not been played with a Cuatro. Even the modern popular songs are using the cuatro (mostly as a reference to the culture) inside their songs
It is an instrument with four single nylon strings, tuned (A D F# B), being the only instrument (that we know) tuned with his last string (B) an octave lower than the other ones.
It’s so similar to the Ukelele that some people refers to it as a “Venezuelan Ukelele”.