Ned to understand why all the idle connections

Hi:

psql (9.6.7, server 11.3) on linux

I have what appear to be a log of idle connections to my DB. Query of
pg_stat_activity indicates well over half (127/206) are like this...

dvdb=# select state_change,wait_event_type,wait_event,state,backend_type
from pg_stat_activity where query = '';
state_change | wait_event_type | wait_event |
state | backend_type
-------------------------------+-----------------+---------------------+-------+------------------------------
2020-04-23 12:57:58.215854-04 | Client | ClientRead |
idle | client backend

What does this indicate?

The vast majority of the connections are through perl/dbi. If a
connection is made, and is currently not doing anything, does it appear in
pg_stat_activity as "idle" ? If, in DBI, $dbh->disconnect is used whenever
the DB is no longer needed, will it disconnect from the DB and NOT appear
as an idle in pg_stat_activity ?

If there are any other column s in pg_stat-activity you'd like to see, or
any other query in any of the system tables, please advise.

Thanks!