I want to know what the different versions of Oracle are. I also want to know what the differences are between all the versions.
There have been many versions of Oracle. The most common versions in use today are Oracle 8i, 9i, and 10g. The Oracle 8i version is now desupported. If you will be implementing Oracle, I would recommend the latest and greatest version, Oracle 10g. Each version contains many new features, too many to enumerate in this forum.
To see a list of new 10g features, check out this Oracle document:
To see a list of new 9i features, check out this Oracle doc: