What does the baseball statistic OBP mean?

Answer 1

It is a combination of 3 different stats. They are OBP/SLG/OPS, which mean

On Base Percentage (OBP)

Slugging Percentage (SLG)

OBP Plus SLG (OPS)

Here is the formula for each one.

On Base Percentage (OBP) is used to determine how often a batter reaches base safely divided by his number of plate appearances.

[Hits (H) + Walks (BB) + Hit By Pitch (HBP)] / [At Bats (AB) + Walks (BB) + Hit By Pitch (HBP) + Sacrifice Flies (SF)]

Slugging Percentage (SLG) is used to determine how much power a batter has

Total Bases (TB) / At Bats (AB)

On Base Percentage Plus Slugging Percentage (OPS) is exactly that:

OBP + SLG

This statistic is used to determine how well-rounded a batter is.

Answer 2

On-base percentage.