lol, Oracle is a a company which makes a database (9i) that is compliant with a SQL standard.
Microsoft makes one called SQL Server
both are databases, databases are used to house information that is related.
a DB ADmin will be reposible for the upkeep of the DB's as well as desgining the tables and dictionaries used in a database. I have found that only after a few design of a DB and then try to write an application that uses it do you really get a feel for how to do it. it can get very complicated going into relational calculaus and algebra. My advice is if you dont even know who oracle is you should probably go to school and learn some comp. sci first. read the trades like eweek to get a better idea of what companies do.