Flat shapes such as squares and octagons have two dimensions and can be easily drawn on paper.
Solids objects such as cubes and prisms occur in three dimensions and are difficult to draw on paper.
Three examples of such solids are shown below.
cuboid

triangular prism

squarebased pyramid

Solids such as these can be described by the number of faces, edges and vertices they have. A face is a flat surface 

12 edges

9 edges

8 edges

6 faces

5 faces

5 faces

8 vertices

6 vertices

5 vertices

Nets
A net is a pattern in two dimensions which, when cut out and folded, will make a solid figure.
Cuboid

Net of a cuboid 
Pyramid

Views of Solids
Solids can be viewed from top, front, back and sides.
For a triangular prism 
View from top

View from front

View from back

View from side

Isometric drawings
Isometric graph paper, which is made up of triangles, instead of the usual squares, can be used to draw views of three dimensional objects. All of the dots on isometric paper are the same distance apart.
e.g. An isometric drawing of the cuboid is shown below.