If you're new to Oracle, you might find it easier to start with
Oracle Express Edition (XE). This is aimed at developers and gives you the core features of Oracle - the RDBMS, PL/SQL, etc - without a lot of the enterprise stuff that you may not need.
Oracle wrote:
Oracle Database 11g Express Edition (Oracle Database XE) is a free version of the world's most capable relational database. Oracle Database XE is easy to install, easy to manage, and easy to develop with. With Oracle Database XE, you use an intuitive, browser-based interface to administer the database, create tables, views, and other database objects, import, export, and view table data, run queries and SQL scripts, and generate reports.
Oracle XE installs a single database, with a SID of "XE", and it pretty much runs itself, so you don't need to worry about all the DBA stuff unless you really want to. There are plenty of
Oracle tutorials on how to get started with Oracle XE. I think Oracle XE plus SQL Developer is a pretty powerful combination for anybody who wants to learn how build applications on top of Oracle.