why does the toast table exist?

I found in my Postgresql 9.0.1 DB as follows:

select oid,relname,reltoastrelid,relpages,relfilenode,reltuples
from pg_class
where oid in ( 90662,90665);

-[ RECORD 1 ]-+-------------------
oid | 90662
relname | audit_trial
reltoastrelid | 90665
relpages | 7713
relfilenode | 373748
reltuples | 930648
-[ RECORD 2 ]-+-------------------
oid | 90665
relname | pg_toast_90662
reltoastrelid | 0
relpages | 0
relfilenode | 373751
reltuples | 0

I have no idea why the TOAST table exists for audit_trial table.

\d audit_trial
Table "public.audit_trial"
Column | Type | Modifiers
------------+-----------------------------+-----------
auditid | integer | not null
userid | integer |
module | character varying(255) |
action | character varying(255) |
recordid | character varying(20) |
actiondate | timestamp without time zone |
Indexes:
"audit_trial_pkey" PRIMARY KEY, btree (auditid)
"audit_trial_action_idx" btree (action)
"audit_trial_actiondate_desc_idx" btree (actiondate DESC) CLUSTER
"audit_trial_module_idx" btree (module)
"audit_trial_userid_idx" btree (userid)*
*