What is ESD protection, Transient Voltage Suppressor Array, diode circuit

 USBLC6 Series 4 Channel 5.25 V SMT Uni-Directional Auto ESD Protection - SOT-23-6

https://www.futureelectronics.com/p/electromechanical--circuit-protection--esd-protection/usblc6-4sc6y-stmicroelectronics-7039237