SABR

Basically
OBP = AVG but with measuring BB's
FIP = ERA sorta, but only measuring HR's and BB's issued
WHIP = a pitcher's version of OBP
SLUG = [ 1B (1) + 2B (2) + 3B (3) + HR (4) ] / plate appearances
WAR = Total player evaluation including offensive WOBA + fielding ratings UZR

• So a player's OBP = AVG, he didn't draw any walks during the game.
• FIP is meant to measure a pitcher's value without any influence of his fielders. That means not measuring how many hits he gives up.
• wOBA is latest SABR version of batting average / OBP. Basically it's takes the slugging percentage formula, but instead assigning 1,2,3,4, to the bases/HR's it assigns [HR (1.70), 3B (1.37), 2B (1.08), 1B (0.77), NIBB (0.62)]. The numerator is still divided by plate appearances.
• The number that is spit out is ugly so they adjust the [HR (1.70),...] values by 15%, to make it look like OBP