A musical score is a copy of a piece of music that shows all of the instrumental parts together, giving a view of the entire piece.
Conductors often work from scores, because they are able to see everyone's part at the same time.
There are different kinds of score that are quite common. For example, a close score , also called short score or condensed score , is a score that has two or more instrumental or vocal parts on each staff. The two-stave format is a commonly used short score type, and looks very much like a piano score. The stem direction seems to break the rule that notes above the middle line must point their stem downward, and notes below the middle line must point their stem upward. It is much more common for voices to perform from a score like this rather than instruments.