RAL lets you mark text up with Bulletin Board Code (BBCode). BBcode is a markup language similar to HTML which allows you to style your text. Text marked up with BBCode will look something like this:
[b]This[/b] text is bold; [color=red]here[/color] is a link to [url]prettyboytellem.com[/url]
As you can see, BBCode tags are enclosed by square braces. Every [tag] which is opened must be closed by a closing [/tag]. Tags sometimes take an optional parameter, like [color=red]. It's up to you to supply valid parameters to the tag.
RAL uses an implementation of jBBCode with some home-baked extensions. If you are accessing RAL over the HTTP(S) interface with a user-agent, the BBCode will be parsed and presented with HTML tags such that it looks pretty in your user-agent. If you are accessing RAL using the API you can typically choose whether or not you want the BBCode parsed by jBBCode.
Implementation on RAL
Overall, BBCode implementations differ from site to site; below is a reference of BBCode tags which are appropriate in the context of RAL.
|[url=param]||Hyperlink||<a href="param">||Optional; valid http(s)://, ftp:// URL|
|[color=param]||Text Color||<span color="param">||Required; valid CSS color|
|[spoiler]||Spoiler text||<span class=spoiler>||N/A|
|[quote=source]||Un/attributed quote||<blockquote cite=source>||Optional; provides a source for the quote|
|[aa]||ASCII Art||<span class=aa>||N/A|
|[sjis]||SJIS Art||<span class=sjis>||N/A|