What is esd, esd protection equipment, Solid state relays, ESD environment

 PGB1 Series 150 V 0.06 pF Bi-Directional 0603 SMT PulseGuard® ESD Suppressor

https://www.futureelectronics.com/p/electromechanical--circuit-protection--esd-protection/pgb1010603mr-littelfuse-8438913