Batting Park Factor
How a ballpark plays for hitters. 100 is neutral.
What it actually is. Batting park factor: how much a ballpark inflates or suppresses offense compared with a neutral one, with 100 as neutral.
What a scout reads off it. The park is a player on every team and this is how it is measured. Coors Field in Denver is the most extreme in the modern game because a mile of altitude takes the break off breaking balls as well as carrying the ball, and that is why Rockies hitters' road numbers look so different from their home ones.
How it lies to you. Park factors are computed over multiple seasons and describe an average hitter, so they overcorrect for some players and undercorrect for others. They are a rough instrument used because the alternative, ignoring the building entirely, is worse.
Batter's Eye: look up anything in baseball