SHOW ALL
The SHOW ALL
command displays the current setting of run-time parameters in 3 columns.
SHOW ALL ;

pg_settings
The pg_settings
view shows the same items as SHOW ALL
but with additional details, across 17 columns versus 3 columns.
TABLE pg_settings ;

pg_file_settings
To read what is stored in the postgresql.conf
file itself, use the view pg_file_settings
.
If freshly written, this file will hold values that may not yet be in effect within the Postgres server. After writing, the settings must be loaded in one of various ways including a server restart.
TABLE pg_file_settings ;

Admin tool
Your databased-administration tool may display these settings.
For example, in pgAdmin 4, choose the cluster name (the Postgres installation) in the navigation panel, click the Dashboard
tab, and in a list bottom panel titled Server activity
, click the Configuration
tab to see a list of your settings.
![screenshot of pgAdmin 4 > [cluster name] > Dashboard > Server activity > Configuration](https://i.stack.imgur.com/qEe8Z.jpg)
Writing
By the way… For info about writing these settings with ALTER SYSTEM
commands, see my Answer on another Question, How to edit postgresql.conf
with pgAdmin 4?.
select * from pg_settings
?