What are some of the features for this database and is it used for companies with 50 or more people? What is a good website that I can find this information?

Oracle 11g, Siebel, PeopleSoft | Oracle, The World's Largest Enterprise Software Company (http://www.oracle.com)

Oracle is one of the top database engines on the market. I believe it's the leader in market share.

Is it used for large or small companies (companies over 50 people)

Yes. While Oracle is primarily used in larger companies, it can be used in smaller applications as well.