Currently i am learning about web hosting, i know that hosting a company web site can provided the email facility, how do they do that?

If I understand you, we are talking about using a third party to host, say, your company's web site and has included some number of email addresses for your company to use? So, you order plan C with web hosting company A. You get the web site, which simply exists on one of the third party's (Company A) many servers. They most likely made you buy or gave you a domain name like www.you.com, for example. They register that URL with their server's IP address, and as part of your deal with them, they write some code to accept say 50 separate email addresses that are in the form of JDoe@you.com. Then you have to go out and get your mail either by downloading it to a server at your site, which probably defeats the purpose of having the third party to begin with, or you set up your employees to go to the third party's server using a mail client like Outlook Express, download it, and everyone at your company gets his/hers intended email from the third party's server. To the outside public, it looks like it's all going on at your office. Hope that's what you wanted. Chris

They give a shared (used by multiple people) or dedicated (used by one person) server.

Servers are just really fast computers. The servers are linked up and a share a massive bandwidth provider like cogent (for like 800$ a month).