Oracle tables starts with BIN$

DROP table puts the tables in recycle bin, and it can be removed from recycle bin by using PURGE command.
The tables in recycle bin can be viewed by 'show recyclebin';

SQL> DROP TABLE RECYCLE;
Table dropped.
SQL> show recyclebin;
ORIGINAL NAME    RECYCLEBIN NAME                OBJECT TYPE  DROP TIME
---------------- ------------------------------ ------------ -------------------
RECYCLE          BIN$FGO4f+kYTnW0fc0rTXSvHQ==$0 TABLE        2014-09-12:19:11:48
SQL>
SQL> PURGE TABLE RECYCLE
  2  ;
Table purged.
SQL> show recyclebin;
SQL>

Detailed description can be found here

http://docs.oracle.com/cd/B19306_01/server.102/b14231/tables.htm#ADMIN01511