In order to know the schema objects please have a look at http://arjudba.blogspot.com/2008/06/database-objects-in-oracle.html
There are some rules to name a schema objects which are defined below.

•Schema name as well as database objects name can be specified within double quotes and without quotes.

•DB_NAME, GLOBAL_NAME, and database link names are always case insensitive and are stored as uppercase. So if you specify these names as quoted identifiers, then the quotation marks are silently ignored.

•Database name can have maximum 8 bytes.

•Database Link name can have maximum 128 bytes.

•Schema name other than DB_NAME and database link name can be 1 to 30 bytes long.

•If an identifier includes multiple parts then each attribute can be up to 30 bytes long.

To know more visit http://arjudba.blogspot.com/2008/07/schema-object-naming-rules.html