Glossary

Here is a glossary of terms I will use. Click on the links. They help.
Offense
wOBA: Weighted On Base Average. It is a linear weights stat, on an On Base Percentage scale.
The formula:

(0.72xNIBB + 0.75xHBP + 0.90x1B + 0.92xRBOE + 1.24x2B + 1.56x3B + 1.95xHR) / PA

For more info, go here.

OBP: On base percentage. It is the percent of the time a player gets on base. Formula: H+BB+HBP/PA

SLG: Slugging percentage. Measures the player's power. Unlike the other stats, the highest slugging possible is 4.000. SLG=TB/AB

OPS: On Base Plus Slugging. OPS=OBP+SLG. It's simple.

OPS +: Adjusted OPS, it is park and league adjusted. 100 is average, below is below average, above is above average. OPS+=100*(OBP/lgOBP + SLG/lgSLG -1)

wRAA: weighted runs above average. Measure of batting runs above average, with 0 being league average. wRAA= (wOBA-lgwOBA)/1.15*PA

BABIP: Batting average on Balls in Play. The name is self explanatory... This is not a skill stat however, it is a luck stat. League average is usually about .300, but if a player is above his usual average BABIP (David Wright, mid 2009) he's in for a bit of a decline as it stabilizes. BABIP=(H-HR)/(AB-HR-K+SF). This is also applicable to pitchers.

WAR: Wins Above Replacement level. It takes offensive, defensive, replacement and positional level stats. Replacement level is a AAA lifer or a guy you can pick up for league minimum. A team full of replacement level players would have 48.6 Wins out of 162 games. I really suggest that you go here to learn more to understand WAR.

Pitching

FIP: Fielding Independent Pitching. This is a stat that measures pitchers on an ERA scale, without defensive interference. It's independent of defense. FIP=(13*HR+3*(BB+HBP-IBB)-2*K)/IP+ a league constant usually 3.2, to get FIP onto an ERA scale.

xFIP: Expected FIP. Replaces HR with flyballs to make it more independent of luck. ONe of the best future performance stats. xFIP = ((FB*.11)*13+(BB+HBP-IBB)*3-K*2)/IP+league constant. Note: .11 is the league average HR/FB which is lgHR/lgFB

ERA: ER*9/IP. Next.

tRA: tRA, and tRA* are maybe the best pitching stats out there. On a run average scale, times by .92 to get to ERA. While I understand the numbers and how its calculated, I don't think I can understand it, so go here.

ERA+: Adjusted ERA. Park and league adjusted. ERA+= (lgERA/ ERA)*100. Below 100 is below average, 100 average, above 100 is average

tRA+: Adjusted tRA. Below 100 is below average, 100 average, above 100 is average. [((lgTRA - tRA) / lgTRA) + 1] * 100

WAR: There is WAR for pitchers. Go to fangraphs glossary to learn about it.

Defense

UZR: Ultimate Zone Rating. Runs saved above average, comapred to position, 0 average, 10 would be 10 runs above average. The primer is here, here and here. Click for a much better understanding.

If I start using a new stat, I'll add it here. This will be available as a link on the side of the blog.