One of the biggest advances of relational databases is to free end users from the need to understand the physical storage of their information. Someone who is simply using the data in an Oracle database has no need to understand the way that Oracle stores its data.
This doesn’t mean that you, as a database administrator, can afford to ignore the way Oracle stores information. Even though Oracle will manage its own physical storage, you can shape the way this space management occurs. To effectively manage an Oracle database, you must understand the way that an Oracle database stores information.