Via reader request, we continue tonight with the statistics short summaries - alliteration is fun - and the subjects are OPS+ and ERA+. Found on every hitter and pitcher's Baseball-reference page, both metrics are quick and simple ways to judge a player's performance.
The base for either stat is 100; if a player has an ERA+ of 102 it means simply that he's 2% better than league average, if one has a OPS+ of 91 he's 9% worse than the league average. Remember absolute value from your math classes and how the teacher stressed that it's simple the distance from 0, well it's almost like that, only 0 in this case equals 100 and defines league average.
For those ambitious ones here are the formulas for each as described on the glossary pages of BR:
lgERA / ERA
BFB stands for park factors, you can find those here amongst other places.