ESD is an acronym for electrostatic discharge. Many times it is used incorrectly as a term for something that is "electrostatic discharge safe." The terms Anti-Static, Conductive, and Dissipative are all terms that subdivide ESD into more detail.

Something insulative is NOT considered ESD safe.
Materials are divided into these terms based on their individual surface resistance. Surface resistance is a measurement of how easily an electric charge can travel across a medium.

Conductive materials are materials that have a surface resistance of less than 1 x 10⁵ ohms/square.

Dissipative items have a surface resistance of more than 1 x 10⁵ ohms/square but less than 1 x10¹¹ ohms/square.

Anti-static materials are generally referred to as any material which inhibits triboelectric charging. This kind of charging is the buildup of an electric charge by the rubbing or contact with another material.

An insulative material is one that has a surface resistance of greater than 1 x 10¹² ohms/square.