There are a number of ways to “export” the table definitions from Oracle. It depends on your desired use. Oracle has an export utility which you can use to export. On a UNIX system, the command is “exp”. There are various options to export just definitions (schema) or both schema and data. The generated file is only usable or “importable” into other Oracle databases, so it has limited value. If you choose this route, be sure to remember that the file is binary and if you transfer or “ftp” the file be sure to select binary mode.
You also could use a number of other facilities to generate files with the table descriptions or to generate table create statements which could be used to create those structures in another SQL based database system.
I suggest working with your Oracle DBA to identify the method and utilities which will best meet your needs.