A landmass, or land mass, is a large region or area of land. The term is often used to refer to lands surrounded by an ocean or sea, such as a continent or a large island. In the field of geology, a landmass is a defined section of continental crust extending above sea level.
land is the part of the surface of the Earth that is solid ground and water. An of land is the area where you are standing on the ground right now. An of land is the plot that your house is located on.