Why does the A320 have an anti skid system and how does it work? Can somebody explain why do A320 aircraft have an anti skid system? What is its purpose? And a brief explanation on how it works.
It's very similar to Anti-Lock-Brakes on cars. 


The main reason aircraft have it is that a locked tyre will heat up, wear excessively and can burst (aircraft tyres are typically run at much higher pressure than cars or even HGVs). 
If you lock a wheel under braking, it no longer provides any steering. Aircraft might not be swerving around obstacles, but staying on the runway is more important than minimising stopping distance.
A locked wheel generates slightly less than maximum stopping force. An automated system can hold the brakes at the point where it's not quite skidding, and brake harder than a human trying not to skid. 


They work by monitoring the speed of each wheel, and releasing the brake on any wheel that slows down significantly more than the rest.

I believe that airliners are tested to check that locked wheel won't wear to the point where it bursts, but you can only do that once!