it's not a symbol (well, it is, in the sense that all letters and typograhical notations are symbols), it's a+e close together, as with other ligatures (http://en.wikipedia.org/wiki/Typographical_ligature) - except, o oops, not:

The character Æ (æ, or aesc) when used in the Danish, Norwegian, or Icelandic languages, or Old English, is not a typographic ligature. It is a distinct letter—a vowel—and when alphabetised, is given a different place in the alphabetic order, rather than coming between ad and af. In modern English orthography Æ is not considered an independent letter but a spelling variant, for example: "encyclopædia" versus "encyclopaedia" or "encyclopedia".

Æ comes from Medieval Latin, where it was an optional ligature in some words, for example, "Æneas". It is still found as a variant in English and French, but the trend has recently been towards printing the A and E separately.[5] Similarly, Œ and œ, while normally printed as ligatures in French, can be replaced by component letters if technical restrictions require it.

I hope the CP works, otherwise you can read that bit by clicking the Wikipedia link. :) In HTML, you can reproduce it by typing (spaces removed)

& a e lig ;

, I would guess, since I type the same but with an o instead of the a when writing the French words that require it, like cœur (French for heart).

/explainy!