First Create Migration for add new fields

php artisan make:migration add_description_to_demo

Then just set the migration up with the details like which col you like to add

Schema::table('demo', function ($table) {
    $table->text('description');
});

Then you can just migrate it:

php artisan migrate

This will allow you to add a column without resetting or rolling back your tables

Thanks Pradeep, will give a try.

@Khushbu Patel You should try this way:

php artisan make:migration update_demo_table

<?php

use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class UpdateDemoTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::table('demo', function (Blueprint $table) {
            $table->text('address')->nullable();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::table('demo', function (Blueprint $table) {
            $table->dropColumn('address');
        });
    }
}

After run below command

php artisan migrate