Difference between Web API Controller and MVC Controller ?

Asp.Net MVC is used to create web applications that return both views and data but Asp.Net Web API is used to create full-blown HTTP services with an easy and simple way that returns only data, not view. Web API helps to build REST-ful services over the MVC only return data in JSON format using JsonResult.

WebApiController:

//POST - Insert Data
public IHttpActionResult PostNewCustomer(CustomerViewModel customer)
{
    if (!ModelState.IsValid) return BadRequest("Invalid data. Please recheck1");
    using (var x=new WebAPIDemo_DBEntities())
    {
        x.customers.Add(new customer() { name = customer.Name, email = customer.Email, address = customer.Address, phone = customer.Phone }); x.SaveChanges();
    }
    return Ok();
}
MVC Controller:
[HttpPost]
public ActionResult Edit(CustomerMvcModel customer)
{
    HttpResponseMessage response = GlobalVariables.webapiclient.PutAsJsonAsync("Customer/" + customer.Id, customer).Result;
    TempData["SuccessMessage"] = "Updated Successfully";
    return RedirectToAction("Index");
}