Para que servem commit, connection, cursor e close?

Exemplo básico

import psycopg2# Connect to an existing databaseconn = psycopg2.connect(""dbname=test user=postgres"")# Open a cursor to perform database operationscur = conn.cursor()# Execute a command: this creates a new tablecur.execute(""CREATE TABLE test (id serial PRIMARY KEY, num integer, data varchar);"")# Pass data to fill a query placeholders and let Psycopg perform# the correct conversion (no more SQL injections!)cur.execute(""INSERT INTO test (num, data) VALUES (%s, %s)"",...      (100, ""abc'def""))# Query the dat