Denatured vs Undenatured Ethanol

• Denatured ethanol (either 95% or absolute) contains additives (such as methanol and isopropanol) that render it unsafe to drink.
• Denaturing refers to removing a property from the alcohol (being able to drink it), not to chemically altering or decomposing it.
• Undenatured ethanol with no other additives or denaturants. Pure Ethanol is often referred to as pure alcohol even though the term "pure" can refer to any proof. Pure Alcohol is considered "pure" regardless of the "cut" of water (proof). Pure Alcohol (Ethanol) is commonly referred to as Beverage Grade Alcohol.

Reference: 

1. http://bitesizebio.com/13518/which-type-of-ethanol-should-i-use/
2. http://chemistry.about.com/b/2014/03/26/what-is-denatured-alcohol.htm
3. http://ethanoltradingcorporation.com/anhydrous-fuel-grade-undenatured-ethanol-(indian-origin