To illustrate the point, compare the process of sending an electronic message via the Internet with Sending a letter by post. The down side to e-mail is that it is such a cheap and easy way to send information to loads of people at once that marketing companies can easily send 'junk mail' and clog up your mailbox. In practice however I haven't found that this happens too often, but if it does there are mail programs which can filter incoming messages and delete those from particular sources or about particular topics. E-mail messages have their own unique qualities and are essentially a different 'beast' from traditional 'snail mail' letters. For example, e-mail messages are less formal in tone, they tend to be shorter and are sent more frequently.
Mail is collected when the person chooses to log on to their computer network or mail server.
Many modern e-mail programs make sending such files effortless and deal with all the complicated bits for you. If you understand URL's then you will understand e-mail addresses, the former points to a file on computer and the latter points to a person who's account is on a computer. The hostname is similar to the street, town and country part of a conventional postal address. From this you can deduce that j.byrne is located in the UK in an academic institution called Glasgow Caledonian University. Most Internet e-mail addresses conform to this layout.