I've gone through this link which is a similar question.
In some places, capacitors are also used for ESD purposes.
In some places, along with capacitors, TVS diodes (or ESD diodes, not sure which term is correct) are used.
Can someone tell me where TVS diodes should be used and where capacitors should be used?
The difference is that ESD diodes have a much lower capacitance; this is often a feature that is advertized.
If you have slow/low-frequency signals, you can afford to put a capacitor directly on the signal line; slowed-down signal edges do not hurt, and will even be useful to prevent EMI.
But if you have high-speed signals, then a capacitor would reduce signal quality too much. So you need a diode to shunt the ESD current into the power supply rails, where it can be eaten by the decoupling capacitor(s).
