Sam, thanks for answering all these questions.
LINE READS: In Rails, dynamic content is generated by templates, which come in three flavors
SUGGESTED LINE: In Rails, dynamic content is generated by templates, which come in three flavors: Embedded Ruby, XML Documents, and RJS views.
If I understand the entire text below correctly, the about sentence refers to XML Documents and RJS views which are mentioned in the following 2 paragraphs. Using the suggested line makes it clearer.