Difference between has_one and belongs_to

Is the difference between has_one and _belongs_to that with has_one
can use the additional parameters such as :dependent and :order? Or is
there more to it then that? Thanks,

It's about where the foreign key sits.

class Foo < AR:Base

if foo belongs_to :bar, then the foos table has a bar_id column
if foo has_one :bar,then the bars table has a foo_id column