I've heard analyst say that a player has been under performing as a batter in the heart of the order many times, or that a bottom of the line up batter has been doing well for its position as of recent.
This makes me believe that each batter in the line up has a specific role. Or at least there are certain league-wide expectations for each position. From what I have noticed, it seems that the heavy hitters are usually in the middle of the order. Also it's obvious that the lead off batter should have high on base percentage (OBP) to increase chances of scoring more runs.
Having said all of that, what are the general characteristics of each batter in the line up?