make query faster??

Hi,
I've a simple query, but when I use *ORDER BY* it takes a long time till I can see the result.

a_nr is varchar(20) and the primary key of my table artikel.

Please, can someone give me a hint, how to improve my query.
Many thanks in advance

-Irina

P.S.: what does *cost=341.63..341.63* mean? I couldn't find an explanation in the archives!

WAWI-# select a_nr,a_bez1,a_bez2,a_bez3,a_bez4,a_gewicht,a_bruttog,kl_ean,a_vol from artikel order by a_nr;
NOTICE: QUERY PLAN:

Sort (cost=341.63..341.63 rows=3809 width=96)
-> Seq Scan on artikel (cost=0.00..115.09 rows=3809 width=96)
EXPLAIN

WAWI=# explain
WAWI-# select a_nr,a_bez1,a_bez2,a_bez3,a_bez4,a_gewicht,a_bruttog,kl_ean,a_vol from artikel;
NOTICE: QUERY PLAN:

Seq Scan on artikel (cost=0.00..115.09 rows=3809 width=96)

EXPLAIN
WAWI=#

In Bruce Momjian's book I read, that indexes are usually not used for ORDER BY operations: a sequential scan followed by an explicit sort is fatser than an indexscan.

What's an explicit sort????????