http://crehgvxpuffkun4nvxneikw3m436hhqkvbkt7peoxa6o2p4lfoffz6ad.onion/help/forum/technical/bbcode?lang=en-us
With it, text like this and this can easily be expressed, among other things. The syntax is composed of 'tags,' like [b] and [u], each with a 'closing' counterpart, [/b] and [/u] in this case. When these tags surround some text, as in [b]this[/b], they change the way it looks.