The Oracle Data Dictionary contains information about data base objects, users and events.  You can access this information through these views of the data dictionary.

||View||Description
|[USER_ROLE_PRIVS]|Roles granted to the user.
|[USER_TABLES] aka TABS|Description of the user's own tables.
|[USER_TAB_COLUMNS] aka COLS|Columns of user's tables, views and clusters.
|[USER_TAB_PRIVS]|Grants on objects for which the user is the owner, grantor or grantee
|[USER_VIEWS] |Test of views owned by the user. 
|[USER_TRIGGERS]|Descriptions of the user's triggers
|[USER_OBJECTS] aka OBJ|Objects owned by the user
|[USER_INDEXES] aka IND|Description of the user's own indexes
|[USER_IND_COLUMNS]|Columns of the user's indexes or on user's tables
|[USER_SEQUENCES]|Description of the user's own sequences
|[USER_SOURCE]|