Oracle has quite a few built in packages available for PL/SQL developers to use. Some packages are optional for the database and must be manually installed. You can find information on the built in packages at Tahiti dot Oracle dot com. Look under Application Development, then SQL and PL/SQL, and finally PL/SQL Packages and Types Reference.
If you are not planning any commercial uses for it, Oracle allows you to download, install, and use any version of their databases. The Express Edition of Oracle is a good choice for basic Oracle database needs. It was created in response to the open source databases available now. It competes with MySQL for example. It has a 3TB maximum size limit. And it is completely free for any type of use.
Normally the exceptions raised by a package are defined by it. However generic errors sometimes cause a package to raise an exception that it does not define. One sample package is UTL_FILE. As you can imagine, it is used for file input/output. Note that you will probably not want to use this package to output reports. There is other software specialized for that purpose.
Another package available is UTL_MAIL. It works with an SMTP server. The package itself does not actually send email. The SMTP server does that. Note that this package is not installed by default during an Oracle install. You must manually install and configure it to work with your SMTP server.
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