As with all other attributes of database objects, you can find out more about the way your tables and indexes work with free space through several data dictionary views.

The USER_TABLES and USER_INDEXES data dictionary views have columns that store the values for the storage parameters that apply to the amount of free space in their particular objects. The USER_TABLES view contains columns for PCT_FREE and PCT_USED, while the USER_INDEXES view only has a column for the PCT_FREE value.

Freelists are lists of free data blocks for a database table or index. The USER_SEGMENTS view has information about the number of freelists allocated to a segment for an object, while the USER_TABLES and USER_INDEXES views have information about the number of freelists allocated to their particular objects.
The USER_TABLES and USER_INDEXES views also have columns for the NUM_FREELIST_BLOCKS, which give the number of blocks on the freelist for the object, and the AVG_SPACE_FREELIST_BLOCKS, which give the average amount of space for each of the freelist blocks.

Click the Quiz link below to answer a few questions about free space.
Free Diction Quiz