Does PostgreSQL automatically generate an id for every row?

When I was started work on the PostgreSQL, crating first time a table, I become stuck on the Identity column because I was familiar with the MS SQL Server. So, first of all, I search the question, "Does Postgres automatically generate an id for every row?". 
The answer is Yes.
There are several ways you can generate the identity column in PostgreSQL, and some examples are given below

1- SERIAL and BIGSERIAL

Using serial and bigserial you can generate the identity column
Example:

--For the SERIAL
CREATE TABLE employee
(
       empid serial NOT NULL,-- It's generate for the int
       name text,
       address text,
       constraint pk_employee_empid Primary key(empid)
);
--Insert some records
INSERT INTO employee(name,address)VALUES('Naina','Noida');
INSERT INTO employee(name,address)VALUES('Ashish','Delhi');
--Now select statement
SELECT * FROM employee;


In result you can see the ID is auto generates and increment by one
Result:


Same thing will happen with bigserial

--For the BIGSERIAL
CREATE TABLE employee
(
       empid bigserial NOT NULL,-- it generate for the bigint
       name text,
       address text,
       constraint pk_employee_empid Primary key(empid)
);



2- GENERATED ALWAYS AS IDENTITY

Using GENERATED ALWAYS AS IDENTITY key we can generate the identity column, it automatically assign a unique value to a column which introduced as a new feature in PostgreSQL version 10.
Run the following query to re-create the employee table.


DROP TABLE IF EXISTS employee;
CREATE TABLE employee
(
    empid INT GENERATED ALWAYS AS IDENTITY,
    name text not null,
       address text,
       constraint pk_employee_empid Primary key(empid)
);
Insert some records
INSERT INTO employee(name,address)VALUES('Naina','Noida');
INSERT INTO employee(name,address)VALUES('Ashish','Delhi');


Result:


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