The RC paper consists in an alpha cellulose base paper on whose both sides polyethylene is extruded (hence the name), and a microporous top coating is applied for the printability.
The first RC papers date back from the 1960's and were aimed at speeding up the development and picture fixing for silver halider papers, thanks to the waterproof properties of the base.
The RC papers became also very popular for digital printing, but specifically modified in order to be printed with dye or pigment-based inks.