The term for the part of the Earth's surface that is not covered by oceans is "continental crust" or simply "landmass". The Earth's crust is divided into two types: the oceanic crust, which is covered by ocean water, and the continental crust, which includes the landmasses of the world. So, the continental crust is the scientific term for the part of the Earth's surface that is not oceans.

No, it's land. The Earth is covered by land and water. Under the water there isn't land, but "the ocean floor" or the sea floor."

Land and sea. That is completely correct. You could call it landmass, but we tend to call it land.