The term “hosting” does not describe a single service, but a variety of services which offer various functions to a domain name. Having a site and emails, as an illustration, are two separate services though in the general case they come together, so most people consider them as one single service. In reality, each domain has a number of DNS records called A and MX, which show the server that deals with each particular service - the first one is a numeric IP address, which specifies where the website 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 name. As an illustration, an A record is 22.214.171.124 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 Internet domain has and the traffic/message is first directed to that company. In case you have custom records on their end, the Internet browser request or the e-mail will be directed to the correct server. The concept behind working with separate records is that the two services employ different web protocols and you can have your site hosted by one service provider and the e-mails by another.