whats the difference?

A brief explanation; the difference between the two is similar to differentiating a fiddle and a violin......

"Resonator, resophonic or Dobro guitars ......
Similar to the flat top guitar in appearance, the sound of the resonator guitar is produced by a metal resonator mounted in the middle of the top. The physical principle of the guitar is therefore similar to the banjo. The original purpose of the resonator was to amplify the sound of the guitar. This purpose has been largely superseded by electrical amplification, but the resonator guitar is still played because of its distinctive sound. Resonator guitars may have either one resonator cone or three resonator cones. Three-cone resonators have two cones on the left above one another and one cone immediately to the right. The method of transmitting sound resonance to the cone is either a "biscuit" bridge, made of a small piece of hardwood, or a "spider" bridge, made of metal and larger in size. Three-cone resonators always use a specialized metal spider bridge. The type of resonator guitar with a neck with a square cross-section – called "square neck" – is usually played face up, on the lap of the seated player, and often with a metal or glass slide. The round neck resonator guitars are normally played in the same fashion as other guitars, although slides are also often used, especially in blues. "

Peace and Guitars,
SouthPaw41L