Permissions Lvl - Can't get the concept

Hey guys,

I know that there is a explanation here:

but it seems I can’t really understand the concept.

Can someone give a alternative explanation ?

The thing I am trying to do is in a Custom DocType a specific field must be shown only to a specific DocType Role.

Ty all

First of all this is not related to v7.
Second if you are looking to deny someone to read a specific field that is where the field level permission come into play.
So generally speaking all fields are LVL0 (Lowest) and anyone who has a READ right for a document can READ LVL0, now if you make perm level of a field as LVL1, then only those users who have read access to LVL1 would see (READ) that field.

I hope it clears the concept.

Ty for your answer