Solid Geometry
Solid Geometry is the geometry of threedimensional space, the kind of space we live in ... 
Three Dimensions
It is called threedimensional, or 3D because there are three dimensions: width, depth and height.


There are two main types of solids, "Polyhedra", and "NonPolyhedra":
Polyhedra
A polyhedron is a solid made of flat surfaces. Each surface is a polygon. Examples:
NonPolyhedra
Some solids have curved surfaces, or a mix of curved and flat surfaces (so they aren't polyhedra). Examples:
Properties
Solids have properties (special things about them), such as:
 volume (think of how much water it could hold)
 surface area (think of the area you would have to paint)
