Oracle PL/SQL/System Tables Views/V FIXED TABLE
Querying V_$FIXED_TABLE shows internal data dictionary structures.
SQL> select name, type
2 from sys.v_$fixed_table
3 where type = "TABLE"
4 and rownum < 6
5 /
NAME TYPE
------------------------------ -----
X$KQFTA TABLE
X$KQFVI TABLE
X$KQFVT TABLE
X$KQFDT TABLE
X$KQFCO TABLE
5 rows selected.
SQL>