Difference Between ViewBag & ViewData

Controller

[HttpGet]

        public ActionResult HerbyList()

        {

            HerbyModel hm = new HerbyModel();

            ViewData["HerbyList"] = hm.Herb;

            ViewBag.HerbyList = hm.Herb;

            return View();

        }

 View

//   this.GridView1.DataSource = (DataTable)ViewData["HerbyList"];

            this.GridView1.DataSource = ViewBag.HerbyList;

            this.GridView1.DataBind();