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