I have here one LCD monitor and has three wired power cable.

1. what is the point of that with that plastic body?

2. What should be that ?!

https://ibb.co/jJVy466

thanks in advance

 

Regulations. There was a time in the US when low mains voltage (i.e., about 110 V) was almost never "safety" grounded.

 

It may not meet the requirements for a class II device (double insulated) for instance if any metal part is accessible outside the case - e.g video or antenna connections.

 

I have here one LCD monitor and has three wired power cable.

1. what is the point of that with that plastic body?

2. What should be that ?!

https://ibb.co/jJVy466

thanks in advance

The housing might be plastic but a metal frame plus electronics inside could produce radiation and a gnd could be used to reduce radiation ( spikes back into the mains).
Picbuster