The word “hosting” does not describe one service, but a set of services which offer numerous functions to a domain address. Having a site and emails, for instance, are two separate services even though in the general case they come together, so a lot of people consider them as one single service. In reality, each and every domain name has a number of DNS records called A and MX, which show the server that handles each specific service - the former is a numeric IP address, that defines where the site for the domain address is loaded from, while the latter is an alphanumeric string, which shows the server that handles the e-mails for the domain. As an illustration, an A record would be 126.96.36.199 and an MX record is mx1.domain.com. Every time you open a site or send an email, the global DNS servers are contacted to check the name servers that a Internet domain has and the traffic/message is first forwarded to that company. If you have custom records on their end, the browser request or the e-mail will then be sent to the correct server. The idea behind working with separate records is that the two services work with different web protocols and you may have your site hosted by one provider and the emails by another.