The definition of “hosting” does not describe a single service, but a number of services that provide a variety of functions to a domain address. Having a website and emails, for example, are two individual services although in the general case they come together, so a lot of people see them as one single service. In fact, each domain has a number of DNS records called A and MX, which show the server that deals with each specific service - the former is a numeric IP address, which identifies where the website for the domain name 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 example, an A record is 126.96.36.199 and an MX record is mx1.domain.com. Each time you open a website or send an email, the global DNS servers are contacted to check the name servers that a domain address has and the traffic/message is first forwarded to that company. In case you have custom records on their end, the Internet browser request or the email will be forwarded to the correct server. The idea behind working with separate records is that the two services employ different web protocols and you could have your website hosted by one service provider and the e-mails by another.