TVS is similar with MOV(Metal Oxidation Varistor), it is normally reverse connected in circuit to protect afterwards circuit. When transient over voltage happens, it operates in avalanche mode, the dynamic resistance is very small to bleed the surge current. And absorb the transient energy with heat. TSS(Thyristor Surge Suppressor) is similar with GDT(Gas Discharge Tube), it is a crowbar device. The standoff voltage can be vary from several tens to hundred, while on state voltage is only several volts. And surge current can be up to several hundred to thousands amperes.

TVS benefit is small volume, high transient power, quick response time, no noise, low cost etc. It is widely used for home appliance, electronic instrument, meter, accurate equipment, computer, telecom, RS-232 line, RS-485 line, CAN bus, LIN bus, ISDN, multiple I/O port, IC circuit, Audio/Video input, AC/DC power, motor, relay noise suppression etc. TVS can be used to protect induced lightning, switching disturb or other human incorrect action. 

There is no voltage ring used for MESA chip, while planner process need voltage ring especially for voltage higher than 600V. Chip area can be consumed additionally with these voltage rings used. Groove etch and Groove passivation is needed for MESA process. MESA process is vertical PN breakdown, and reliability is higher.

ESD diode is normally parallel connect with circuit which need be protected. In normal condition, ESD does not work, it is high impedance, it will not impact circuit normal operation. When ESD or transient surge happens, over voltage will make it from high impedance to very low impedance to bleed transient current and keep the clamp voltage to a safe level to protect afterwards circuit. The device will be recovered to high impedance with the transient over voltage disappears. 

Thyristor can be used for high voltage, high current switching with small gate voltage, current control. The benefit is small volume, light weight, low power dissipation, high switching speed. It is widely used for non-contact switch, controlled rectifier, inverter, voltage and motor speed dimmer.

Reverse breakdown voltage, Max clamp voltage, transient pulse power, PN junction capacitance, response time etc. TVS response time is very quick, normally is ps level. It is most fast among those transient voltage suppressor devices. You don't need worry about its response time when you use it for electronic circuit transient over voltage protection.

ESD do damage the electronic equipment severely or operation malfunction. There are two  ESD damages, one is dominance and the other is recessive. Recessive damage cannot be found immediately, but the device is becoming fragile. It will be easier to be damaged under over voltage or high temperature condition. There are two failure mechanism for ESD: One is ESD current make the device failure by its heat accumulation. The other is ESD high voltage make the isolation breakdown.

Zener voltage breakdown normally happened below 6V, because of its high concentration of P and N. And its PN exhaust layer is very thin, carrier can be transited through PN junction by tunnel effect. Avalanche breakdown happened for those voltage higher than 6V, its PN exhaust layer is thicker, carrier will strike each other through PN junction like a snowslide. Zener diode is normally used for those low current and low voltage stabilization.