This manual will get technical pretty quick: but let's start with the broadest strokes.
Bookworm is an open-source platform that's designed to help expose large platforms of texts online with the following philosophy:
Curators of texts could take the simplest possible route and simply post scans of old documents. In the case of handwritten documents, this is sometimes the only thing it's reasonable to do (unless you have the budget to hire a whole bunch of transcribers, or the time to do it yourself). But usually, this isn't enough. Search engines are the next obvious step: but while search engines are great for finding particular sets, they're quite bad at helping users to understand the scope and contents of a collection as a whole.