What are XOOPS codes?

If reffering to the xoops codes radio button in (for example) the comment form: With this option enabled tags like: [i'][code'][b'] can be used. If disabled, these tags will be shown as plain text.

This Q&A was found on XOOPS Web Application System : https://xoops.org/modules/smartfaq/faq.php?faqid=567