The i version started from 8i onwards. It stands for oracle internet. Because till then (in version 8)it did not support data transfer over the internet. At that point of time use of internet was not widely used. Next was 9i with some of the enhanced features of 8i. Next was 10g, it stands for Oracle GRID,because it supports grid architecture.
10g follows Oracle’s 9i platform. Oracle says that the g (instead of the expectedi) in the name symbolizes the company’s commitment to the grid model.
Next in database is 11g which is basically a ERP.