Have you ever tried to get the words '2-D' and '3-D' while dealing with Geometric shapes? The letter "D" stands for Dimensional and the number defines the count of dimensions it has. In simple terms, 2-D shape defines that it has two sides joined at each vertex (corner). 3-D shape defines that it has three sides (or faces) joined at each vertex (corner). The 2-D shapes has the length and the width where as the 3-D shapes has the length, width and the height. We can say that 3-D shapes has depth. They are solid shapes. It has edges, vertices, faces and the Base. The edges are the lines where the the faces intersect each other. The faces are the sides of the figure. The Vertex (plural:vertices) are the corners of the figure. The base is the bottom side of the figure.
The 3-D shapes are called by its base.
Cube: The cube is a 3-D figure with six square sides of the same size. It has a square at the base.
Prism: A solid with parallel congruent bases which are both Polygons. A Rectangular prism has rectangle at the base, hence its name. Similarly, a Triangular prism has triangle at the base.
Pyramids: Pyramids are also named after its base. A Square Pyramid has Square at the base. A Pentagonal Pyramid has Pentagon at the base. All the lateral sides/faces of the pyramids are triangles.
Cylinder: A cylinder is a tube with long straight sides and two equal sized circular ends. It has NO vertex.
Cone: A cone is a solid shape which has a circle at the base which narrows to a point. It has ONLY ONE vertex.
Sphere: It is just like a round ball (example: football). It has NO vertex, NO side, NO edge.
A NET for a geometric solid is the 2-D pattern for constructing the 3-D shape. Cut and open a 3-D shape and check for the 2-D shapes aligned. That's the net of the given figure. A cube has three squares vertical and 3 squares horizontal joining to the middle square. Sometimes, they may give you the top view, front view, back view and the bottom view, and a question may be asked to find the 3-D figure formed by them. You will get the idea of solving these problems once you get practice in identifying the net for the solid boxes.