Access Token and Developer Token

Hello,

 I am new to box. Working only with .net sdk.

 have created the app in the "Box developer". I had seen Access token and refresh token (I had seen it earlier, but I do not see it anymore). I however have noted both of them can I use them?. I see a developer token that has to be created every hour, what is the difference between developer token and access token.

I tried enumerate the files from my box account. I got the following error 

"The API returned an error [InternalServerError | 1ff9eb6346e5f3c86613144bc4a46e3ac.1ff9eb6346e5f3c86613144bc4a46e3ac] internal_server_error - Authorization Failed"

Here is the .net program.

static void Main(string[] args)
{
     Console.WriteLine("Enter token:");
     string token = Console.ReadLine();

     var auth = new OAuthSession(token,
               "WnzLeadQiJ89fYilR1xyYJvmMKxONt5i0N8CFYnT0hbbVerrq9Y3DSUV2C1HPrtq",
                3600,
                "bearer");

     var config = new BoxConfig(string.Empty, string.Empty, new Uri("http://localhost"));

     var client = new BoxClient(config, auth);

     Task t = MainAsync(client);
      t.Wait();

}
private static async Task MainAsync(BoxClient client)
{
     try
     {
          var coll = await client.FilesManager.GetFileTasks("0");
     }
     catch (Exception ex)
     {
          throw;
     }
}

I used the developer token for the access token.

Can you please let me know where was access and refresh token which I do not see now.

Thanks,

Subhash