Electrostatic discharge is important in situations involving danger of explosion (explosives, chemicals, gases, dust explosion), or if you work with sensitive electronics (microchips, hard drives, etc.). When you move, friction always causes an electrostatic charge in your body. Shoes and clothing that are not conductive (enough) can increase this charge.
Anti-static shoes have an electrical resistance between 0.1 and 1000 MegaOhm (MΩ), measured according to EN 20344: 2011 5 10. This value is a compromise between good protection from electrical shocks and sufficient dissipative capacity. These shoes may be worn in many different work environments.
ESD-shoes (ElectroStatic Dissipative) have an electrical resistance between 0.1 and 100 (MΩ), measured according to BS EN 61340-4-3: 2002 (IEC 61340-4-3:2001). ESD shoes are thus guaranteed to have an extremely low electrical resistance under any conditions in order to prevent a strong, uncontrolled electrostatic charge.