Oracle Linux is an open-source operating system, I would recommend you to first install Oracle Linux on your test environment and start practicing that's the only way to learn.
Oracle Linux can be downloaded through Oracle's E-delivery service or from a variety of mirror sites.
Please check the below link to DL and find out more about Oracle Linux.
https://linux.oracle.com will provide you with links to documentation and Oracle Linux specific information. Beside the Oracle UEK kernel, Oracle Linux is based on Red Hat Enterprise Linux and information you find for RHEL should be good. If you need more specific help, please ask more specific questions, for instance, what are you interested in learning, such as installing, configuring for Oracle database products, shell scripting, etc.
Thank you both guys....
i have installed 6.4 desktop version on virtual box and now i am stuck,how to install browsers, softwares, basic commands( i am from windows background don't know even a single command), first i want to play with it to become familiar then will install oracle db etc what it is build for.
The standard installation package manager is the yum utility, which unlike rpm resolves software dependencies and prevents you from damaging your system. You can use yum to query and install software. For example:
yum list *rdbms*
yum provides /bin/ls
yum search perl
yum info oracle-rdbms-server-12cR1-preinstall
yum install firefox
After installing the appropriate prerequisite package you can use ssh with X forwarding to display the Oracle universal installer (OUI).
yum install oracle-rdbms-server-12cR1-preinstall
mount /dev/cdrom /mnt
ssh -X oracle@localhost