The definition of “hosting” doesn't describe a single service, but a variety of services that offer numerous functions to a domain address. Having a site and e-mails, as an illustration, are two independent services even though in the general case they come together, so a lot of people consider them as one single service. The truth is, each and every domain name has a couple of DNS records called A and MX, which show the server that manages each particular service - the first one is a numeric IP address, that identifies where the website for the domain is loaded from, while the latter is an alphanumeric string, which shows the server that handles the e-mails for the domain name. As an example, an A record would be 123.123.123.123 and an MX record would be mx1.domain.com. Whenever you open a site or send an e-mail, the global DNS servers are contacted to check the name servers that a domain has and the traffic/message is first forwarded to that company. If you have custom records on their end, the Internet browser request or the email will be directed to the correct server. The concept behind employing separate records is that the two services use different web protocols and you could have your site hosted by one service provider and the e-mail messages by another.