Complex sentence: In configurational languages, the subject of a sentence is outside the VP (directly under S below) and the object is inside; in non-configurational languages, since there is no VP constituent, there is no structural difference between subject and object.
Split into simpler sentences: In configurational languages in contrast, the subject of a sentence is outside the VP (directly under S below) but the object is inside it. In non-configurational languages, since there is no VP constituent, there is no structural difference between subject and object.