Databases are all about saving data. With DBMS and RDBMS, the entire data became relational and all the records became related to each other as in the real world. So came into existence the concepts of primary keys, foreign keys, foreign key constraints and whole bunch of other terms like composite keys, referential integrity, indexes and what not.
Nicest way to install Oracle XE on any operating system (for development) is Docker. Docker is an application container for Mac, Linux and Windows. It is based on LXC and gives you the ability to package complete application including their dependencies to a self-containing file (called an image). These images can be exchanged and run on every Linux machine where Docker is installed! Awesome!