Waxed paper, wax paper, or greaseproof paper was invented by Thomas Edison. It is a translucent paper which has been coated with wax on both sides, rendering it moisture resistant and non-stick. It is moisture resistant, but not waterproof, so it will be compromised by contact with liquid. It's also not heatproof, as the wax begins to melt at a relatively low temperature.
Once upon a time waxed paper was widely used to wrap foods like sandwiches and to line cake pans. Today its wrapping utility has been surpassed by plastic wrap and tin foil, and it's rapidly being eclipsed by parchment paper in the field of baking because waxed paper can be used in the oven only if its surface is completely covered and protected from direct heat. So you can line a cake pan with waxed paper to stop the cake from sticking to the pan because the batter covers and protects the paper, but you can't line a cookie sheet with waxed paper when making cookies, because the exposed parts will burn. Parchment paper, on the other hand, is heat resistant.