The information supplied with the question is incomplete and a worthwhile answer cannot therefore be provided.
the definition of 2D is it is flat on the piece of paper -A design
A chart or a map.
The way the 3 dimensional earth is shown on a flat piece of paper.
No. The square is all on one flat surface, like a piece of paper, but a cube has height off of the paper. When you set the cube down on the piece of paper, the place where it touches the paper is a square, but there's a lot more to it than that.
It's any figure that you can draw on a flat piece of paper or carve into your desktop.
A flat piece of paper is 2D. A cube is 3D. Therefore the drawing of the cube is a representation.
the definition of 2D is it is flat on the piece of paper -A design
It is a drawing of the earth on a flat surface
A chart or a map.
It is a drawing of the earth on a flat surface
a map
Both "sheet of paper" and "piece of paper" can be correct, but they are used in different contexts. "Sheet of paper" refers to a single flat piece of paper typically used for writing or drawing, whereas "piece of paper" can refer to a smaller portion or fragment of a larger sheet.
Projection
The way the 3 dimensional earth is shown on a flat piece of paper.
A map represents all parts of the Earth's surface on a flat piece of paper. Maps use projections to depict the curved Earth's surface on a 2-dimensional plane.
Cartographers an represent the spherical Earth on flat paper by making a projection, which is like casting shadows from the spherical world onto a flat piece of paper.
A projection