explain following code step by step?

protected void GridView1_RowUpdating1(object sender, GridViewUpdateEventArgs e)
   {
       int row = GridView1.EditIndex;
       GridViewRow rows = GridView1.Rows[e.RowIndex];
       if ((((TextBox)rows.FindControl("txtuser_name") != null) && (TextBox)rows.FindControl("txtpassword") != null))
       {
           int id = Convert.ToInt32(GridView1.DataKeys[row].Value.ToString());
           TextBox txtuser_name = (TextBox)rows.FindControl("txtuser_name");
           TextBox txtpassword = (TextBox)rows.FindControl("txtpassword");
           string user_name = txtuser_name.Text;
           string password = txtpassword.Text;
           con.Open();
           SqlCommand cmd = new SqlCommand("update login set user_name='" + user_name + "',password='" + password + "' where user_id=" + id + "", con);
           Page.ClientScript.RegisterStartupScript(this.GetType(), "msg", "<script>alert('Record Updated')</script>");
           cmd.ExecuteNonQuery();
           GridView1.EditIndex = -1;
           con.Close();
           bind_login();

       }
   }