Why there's an @ in your email address.
In 1971, programmer Ray Tomlinson sent the first email between two ARPANET computers standing side by side. He needed a character to separate user from machine that appeared in no name. On the keyboard he found the rarely used @. He forgot the content of that first message himself, probably something like "QWERTYUIOP".
Useful: Good conventions are often just the most pragmatic choice that happened to stick.
Source: en.wikipedia.org