Parametric/Surface Modeling and 3-D Solid Modeling

Write the following definitions down in your notebooks before you do your practice. 
3D CAD modeling can be classified into 3 distinct categories:

• Wire-frame modeling
• Surface modeling
• Solid modeling

Wire-frame models are undoubtedly the least complicated when compared to the other two categories. In a wire-frame model, all the surfaces of the physical object (including the opposite ends and internal components) are represented through bare lines and arcs. Due to the simple drawing techniques used in wire-frame models, they may not be suitable for complicated projects that require uncompromising realistic effects.
Surface models are more realistic than wire-frame models, but not nearly as much as solid models. Unlike wire-frame models, they are created by merging 3D surfaces instead of bare lines and arcs. A three-dimensional surface is more like a piece of paper that can be placed at various angles to specify different shapes. So basically, in surface modeling, designers join multiple surfaces to give it the desired shape as well as to hide the backgrounds that need not be seen.
Solid models are vastly different from the other two types of models on the ground that they are solid inside. In other words, solid modeling can be referred to as a technique used to combine a number of "solid objects" into a single 3D design. Much like a physical object, a solid model also has additional properties like density, weight and center of gravity because of which it is most preferred choice when it comes to designing prototype of a mechanical product.