what does enable means in create table?

[marist89]

SQL> create table t1 (f1 number not null enable);

Table created.

SQL> create table t2 (f1 number not null disable);

Table created.

SQL> select table_name, constraint_name, constraint_type, status
  2  from user_constraints;

TABLE_NAME                     CONSTRAINT_NAME                C STATUS
------------------------------ ------------------------------ - --------
T1                             SYS_C001568                    C ENABLED
T2                             SYS_C001569                    C DISABLED

SQL> insert into t1 (f1) values (null);
insert into t1 (f1) values (null)
*
ERROR at line 1:
ORA-01400: cannot insert NULL into ("MARIST89"."T1"."F1")


SQL> insert into t2 (f1) values (null);

1 row created.

SQL> commit;

Commit complete.