What causes a psycopg2.OperationalError when connecting to a PostgreSQL server?

Question

Python

Hello. With PostgreSQL, as well as in principle with the DBMS, I am familiar only in theory. Now I am practicing.
When trying to create a connection by the PostgreSQL database server in the following way

def create_connection():
    connection = psycopg2.connect(
        dbname='database',
        user='postgres',
        password='password',
        host='localhost',
        port='5432'
    )

The following error appears
File "C:\Program Files (x86)\Python38-32\lib\site-packages\psycopg2\__init__.py", line 127, in connect
conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
psycopg2.OperationalError
Can't figure out why. Who will tell?