As you wander around SB Nation during baseball season, you are going to see a lot of these:
Do not be afraid! If you know what you are looking at, continue going about your day. If not, a brief explanation follows the jump.
What you see is a win probability chart, and it's nothing crazy.
Think of it as more of an advanced scoreboard. Each event in a baseball game adds to one team's chances of winning, and detracts from the other's. These charts look at the result of every play, and present how often in the typical baseball game a team is going to win after that play. It assumes everything, including talent, is equal, so there is stuff missing, but it simply gives you a nice idea of how much that home run in the second inning, or that strikeout in the seventh inning actually affected a team's chances.
Plus, it looks cool.
Fangraphs has a nifty scoreboard every day with every game, and if you click on the game itself, you can get a full boxscore. Included is a player's total contribution in terms of win probability added or subtracted.
That's all there is to it. If you want to understand more than just how to look at the chart and go "oh," then you can start with this link right here. And if you're really interested, Baseball-Reference has historical graphs, so you can look at the charted drama of, say, Game Seven of the 1991 World Series.
You may now return to your regularly scheduled day.