I started playing the dobro (resonator guitar) in a Jam of Blue Grass music in Madrid.
It is an acoustic guitar whose sound is produced by one or more resonator metal cones instead of the harmonic cover. They usually call it "Dobro" because the first brand that marketed them was called dobro. It was designed to offer a greater amount of sound than acoustic guitars, which were in trouble when playing alongside percussion and wind instruments in the orchestras.
There are two types of masts:
Rounded mast. They are intended to be played like a conventional guitar and are often used in blues.
Square mast. Designed specifically to be played Lap Steel style in blue grass, country, blues.