What is Details view in asp.net??? with all related operations

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;

public partial class DetailsView : System.Web.UI.Page
{
    SqlConnection con1 = new SqlConnection("Data Source=tops17;Initial Catalog=Grid_DetailsView;Integrated Security=True;Pooling=False");
    protected void Page_Load(object sender, EventArgs e)
    {
        con1.Open();
        if (!IsPostBack)
        {
            Fill_Details();
        }
    }
    public void Fill_Details()
    {
        SqlDataAdapter sda1 = new SqlDataAdapter("select * from tbl_reg",con1);
        DataSet ds1 = new DataSet();
        sda1.Fill(ds1);
        DetailsView1.DataSource = ds1;
        DetailsView1.DataBind();

    }
    protected void DetailsView1_PageIndexChanged(object sender, EventArgs e)
    {
        DetailsView1.PageIndex = e.NewPageIndex;
        Fill_Details();
    }
    protected void DetailsView1_ModeChanging(object sender, DetailsViewModeEventArgs e)
    {
        DetailsView1.ChangeMode = e.NewMode;
        Fill_Details();
    }
    protected void DetailsView1_ItemUpdating(object sender, DetailsViewUpdateEventArgs e)
    {   int id1=1;
       int id1 = int.Parse(DetailsView1.FindControl("labelid").tostring());
        TextBox txtf = (TextBox)DetailsView1.Rows[id1].FindControl("txtfirst");
        TextBox txtl = (TextBox)DetailsView1.Rows[id1].FindControl("txtlast");
        TextBox txte = (TextBox)DetailsView1.Rows[id1].FindControl("txtemail");
        TextBox txtm = (TextBox)DetailsView1.Rows[id1].FindControl("txtmobile");
        TextBox txta = (TextBox)DetailsView1.Rows[id1].FindControl("txtadd");
        TextBox txtlo = (TextBox)DetailsView1.Rows[id1].FindControl("txtloc");
        TextBox txtu = (TextBox)DetailsView1.Rows[id1].FindControl("txtuser");
        TextBox txtp = (TextBox)DetailsView1.Rows[id1].FindControl("txtpass");
        SqlCommand cmd1 = new SqlCommand("update tbl_reg set firstname='" + txtf.Text + "',lastname='" + txtl.Text + "',emailid='" + txte.Text + "',mobileno='" + txtm.Text + "',address='" + txta.Text + "',location='" + txtlo.Text + "',username='" + txtu.Text + "',password='" + txtp.Text + "' where id='" + id1 + "'", con1);
        cmd1.ExecuteNonQuery();
        con1.Close();
        DetailsView1.ChangeMode(DetailsViewMode.ReadOnly);
        Fill_Details();
       
    }
    protected void DetailsView1_PageIndexChanging(object sender, DetailsViewPageEventArgs e)
    {
        DetailsView1.ChangeMode(DetailsViewMode.ReadOnly);
        Fill_Details();
    }
    protected void DetailsView1_ItemDeleting(object sender, DetailsViewDeleteEventArgs e)
    {
        int id1 = 1;
        SqlCommand cmd1 = new SqlCommand("delete from tbl_reg where id='"+id1+"'",con1);
        cmd1.ExecuteNonQuery();
        con1.Close();
        DetailsView1.ChangeMode(DetailsViewMode.ReadOnly);
        Fill_Details();
    }
}