explain join in postgresql code example

Example 1: psql join

SELECT *
    FROM weather INNER JOIN cities ON (weather.city = cities.name);

Example 2: postgres join

-- This is in postgreSQL

-- We have tableA and tableB, x is primary key in tableA and also
-- a foreign key in tableB as y
SELECT * FROM tableA JOIN tableB ON tableA.x = tableB.y;

-- This will select all the columns from both tables that share a key