What it means
De facto means "in fact" or "in practice", as opposed to de jure ("by law"). It describes something that is true in reality even without official recognition. In Australia the most common use is a "de facto relationship": two people living together on a genuine domestic basis who are not married. Under the Family Law Act, de facto partners (including same-sex couples) have many of the same rights as married couples regarding property and financial matters after separation.
How it's used
After living together for three years, they were treated as de facto partners when dividing their property.