Q:

Why do they separate some parts of PCBs through making wide holes?

I have seen several PCB that they have wide holes in some their parts (especially the supply of circuits parts). for example take a look at this picture:

and on the board:

Not sure but I think it is related to the noise, Is it correct?
If so, it's not acceptable to me because other parts of PCBs aren't conductive then how it can transfer the noise?
If so, how much it can be effective?
And my last question is, do they have any special name?

A:

It's for better high-voltage safety. 
Unrelated, because it's not noise. 
Very. Air is a much better insulator, and it doesn't get wet/have a conductive film form. 
Basically, a circuit board can get dirty and/or wet. This makes the surface of the board slightly conductive, and once it's a bit conductive, electrochemical action can make it very conductive, and then you get a free fire.
Isolation slots / creepage distance cutouts/air gaps.

