This provides person to person communication. It is not quite analogous to the postal service (snail-mail), messages will be delivered to your ISP (Internet Service Provider) who will hold them until you next collect your mail
Although primarily for small quantities of plain (ASCII) text, it is possible to email non-ASCII data as an attachment which can be saved to disk on receipt. There are also sites that operate lists - mail sent to one address is redistributed to subscribers. There is a list for UK&Ireland genealogy.
Email addresses look like mailbox@site but there enormous variations...
Now for File Transfer