The code tag is an html tag that allows web pages to display code. Since most coding in any language involves many metacharacters that mean something in html, displaying code often causes unforeseen errors, as the browser takes these metacharacters to be formatting instructions.
The way around this is with the code tag, which tells browsers to display the characters literally. In this way, it functions a little bit like the \ in Unix.
e2 does not seem to fully support the code tag, as when I write:
The code tag is used so html source can be shown in webpages.
The word "html" shows up in bold, and not as the word html between tags.