This information was included in the introductory email that was sent to you. If you no longer have that email, send an email to support@cheaperwebhost.com with your request. Be sure to include the domain name you are asking about.

All sites hosted by Line of Site provide webmail access to your email so that you can access your mail when away from the office or on holiday. If your site is not hosted by us then this will depend on your hosting company.

Yes. Basically that's what it is generally used for as most use a default email application such as Microsoft Outlook on their primary computer.