field card ruling

sry if this sounds noob but
i need to ask if my opponent has a set field card then i set a field card does his field card get destroyed?
cause some people say will get boomed but if i'm not wrong it doesn't get destroyed right?
unless it is an active field card and i activate another field card

From Wikia :
Only 1 Field Spell Card may be active at any time, and any new Field Spell Card that is activated destroys the other Field Spell Card which was active at that time. You may activate a Field Spell Card if there is one already present on your side of the field. By doing so, the first Field Spell Card is destroyed and sent to the Graveyard. A Field Spell Card may be also be Set here, instead of Activated. If it is Set, and there is already a Field Spell Card on your opponent's side of the field, that Field Spell Card is not destroyed.

There can only be one active Field magic on the field so if you set nothing will happen as only one field magic is active.

thanks