jamie=# create table users ("user" text, "password" text);
  CREATE TABLE
  jamie=# insert into users values ('bob', 'whatever');
  INSERT 0 1
  jamie=# select user, password from users;
   user  | password
  -------+----------
   jamie | whatever
  (1 row)

Is because the name /user/ is a pseudo-function keyword, and is an alias for /current_user/

  test=# select "user", "password" from users;
   user | password
  ------+----------
   bob  | whatever
  (1 row)

Newer versions of PostgreSQL make this more clear:

  test=# select user, password from users;
   current_user | password
  --------------+----------
   postgres     | whatever
  (1 row)

Here is a full list of keywords: https://www.postgresql.org/docs/current/sql-keywords-appendi...