How to create meta or custom field in database in Wordpress without a plugin?

Create meta or custom field in database in WordPress without a plugin

For Create

                        update_user_meta( $user, 'person_name', false);

update_user_meta( $user, 'phone_no', false);

update_user_meta( $user, 'city',false );

For Update

                        update_user_meta( $user, 'person_name', $_POST['person_name'] );

update_user_meta( $user, 'phone_no', $_POST['phone_no'] );

update_user_meta( $user, 'city', $_POST['city'] );