Sending an email via a form

 I'm adding a contact form to my ASP.NET website which will send the content of the textfields to my email inbox.
 What I don't understand is this part of the C# code:
 
smtpClient.Host = "mail.domain.com";
smtpClient.Credentials = new System.Net.NetworkCredential("username@domain.com","Password"); What does it mean by "domain.com"? And what username and password do I give? Do I do something like the following?? smtpClient.Host = "hotmail.com";
smtpClient.Credentials = new System.Net.NetworkCredential("username@ho ...