Let us take a simple example to understand better:

<AddressDetails>
  <HouseNo>4</HouseNo>
  <StreetName>Rohini</StreetName>
  <City>Delhi</City>
</AddressDetails>

This is the XML that has to be deserialized.

  Inorder to deserialize the XML we need to create a class, having variable with same name as that of XML tags.
The values of the XML tags get mapped to their corresponding variable, during desrialization.

 So for the above XML following is the corresponding class:

public class Address
{
    public int HouseNo { get; set; }
    public string StreetName { get; set; }
    public string City { get; set; }
}

Now following is the code packet that will actually map this XML to the class object:

public static void Main(string[] args)
{
    XmlSerializer deserializer = new XmlSerializer(typeof(Address));
    TextReader reader = new StreamReader(@"D:\myXml.xml"); // path where the XML is stored
    object obj = deserializer.Deserialize(reader);
    Address XmlData = (Address)obj;
    reader.Close();
}

Now as we have actually deserialized the XML we can access the XML tag values by:

Address.HouseNo,
Address.StreetName,
Address.City

Hope this helps you... Happy Coding..!