tubs are essentially a tyre and tube stitched together to make an air tight tube, its then glued to the rim.
Advantages are less chance of pinch flats as the rim profile is different, ability to run way lower pressures, ability to still ride on a flat tyre.
Dugast produce the Rhino, but they’ll also sew a riders own choice or sponsors tread onto their own casings.
Most common in cyclocross where amateurs like me use them, quite common in elite XC riders.