Enjoy the beer that you deserve.
Specific gravity is the mass ratio of a solid or liquid material compared to water at 39 degrees Fahrenheit (4 degrees Celsius).
The scale is absolute, so that a specific gravity of 1.065 means than the material is 1.065 the mass of water at the specified conditions. The addition of fermentable sugars to water will increase the mass of the wort, while fermentation of these sugars will decrease the mass of the wort.
It is used commonly to characterize beer and to determine the degree of fermentation that has occurred in the wort.