Viscosity, in simple terms, is the thickness of a fluid.  The higher the viscosity, the thicker the fluid.  Dynamic viscosity is most commonly measured in centipoise (cps).
For example, water is low viscosity (thin) 1 cps, while honey is high viscosity (thick) 2000 cps.

Specific gravity is the relative density of a liquid or solid compared to water. 
For example, table salt has a density 2.16 greater than water.

Here are a couple of links that explain these in more detail:

http://en.wikipedia.org/wiki/viscosity

http://en.wikipedia.org/wiki/specific_gravity