The definition of “hosting” does not describe only one service, but a variety of services that offer different functions to a domain address. Having a website and e-mails, for example, are two independent services though in the general case they come together, so many people see them as one single service. The truth is, each and every domain 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 manages the e-mails for the domain address. For instance, 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 directed to that company. If you have custom records on their end, the browser request or the e-mail will be sent to the correct server. The concept behind using separate records is that the two services work with different web protocols and you can have your website hosted by one service provider and the emails by another.
