True - the density of cork material is much less than the density of wood. I would estimate density of cork around 200 kg/m^3 and density of wood can range 600-900 kg/m^3 .... these are not exact values, these are my estimates, but you can see the large difference in density.

Density tells you how much mass of a substance will fit into a unit of volume. So if you have 1 m^3 of cork and 1 m^3 of wood, that cork's mass would be around 200 kg while the wood's mass would be hundreds of kg higher.