ASP.NET MVC when and how are controller constructors called?

I'm doing a tutorial by book in MVC 4 using Ninject and I understand the concept of binding interfaces to concrete classes with injections, however I noticed that controller constructors usually pass the repositories associated with the bindings. My questions are when and how are the controller constructors fired after I specify a parameter in the constructor, how is that parameter passed? And what if I had overloaded constructors? Maybe I'm not understanding the Controller factory code, but to me it doesn't seem like it happens there, here are my example classes:

Controller:

    using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using SportsStore.Domain.Abstract;
using SportsStore.WebUI.Models;

namespace SportsStore.WebUI.Controllers
{
    public class ProductController : Controller
    {
        private IProductsRepository repository;
        public int PageSize = 4;

        public ProductController(IProductsRepository productRepo)
        {
            this.repository = productRepo;
        }

        public ViewResult List(string category, int page = 1)
        {
            ProductsListViewModel model = new ProductsListViewModel
            {
                Products = repository.Products
                .Where(p=>category == null || p.Category == category)
                .OrderBy(p => p.ProductID)
                .Skip((page - 1) * PageSize)
                .Take(PageSize),
                PagingInfo = new PagingInfo
                {
                    CurrentPage = page,
                    ItemsPerPage = PageSize,
                    TotalItems = category==null?
                    repository.Products.Count():
                    repository.Products.Where(p=>p.Category==category).Count()
                },
                CurrentCategory = category
            };
            return View(model);
        }


    }
}

Controller Ninject Factory:

    using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using Moq;
using Ninject;
using SportsStore.Domain.Entities;
using SportsStore.Domain.Abstract;
using SportsStore.Domain.Concrete;

namespace SportsStore.WebUI.Infrastructure
{
    public class NinjectControllerFactory: DefaultControllerFactory
    {
        private IKernel ninjectKernel;

        public NinjectControllerFactory()
        {
            ninjectKernel = new StandardKernel();
            AddBindings();
        }

        protected override IController GetControllerInstance(System.Web.Routing.RequestContext requestContext, Type controllerType)
        {
            return controllerType == null ? null : (IController)ninjectKernel.Get(controllerType);
        }

        private void AddBindings()
        {
            Mock<IProductsRepository> mock = new Mock<IProductsRepository>();
            mock.Setup(m => m.Products).Returns(new List<Product>{
            new Product { Name = "Football", Price=25},
            new Product {Name = "Surf board", Price=179},
            new Product { Name = "running shoes", Price=95}
            }.AsQueryable());

            ninjectKernel.Bind<IProductsRepository>().To<EFProductRepository>();
        }
    }
}