The section ID is a rather long series of numbers and letters. It uniquely identifies the section and can be used to link to it from any other bookvoid book. Why do we use an ugly identifier like this? It is based on the concept of
org/wiki/Universally_unique_identifier and allows the use of Bookvoid while offline to create new sections without any chance of them having the same ID as an existing one. Almost all data in Bookvoid is identified this way which enables content creation of things like user notes to be performed while offline. It is invisible to users for most kinds of data but since you need to be able to reference sections to insert them in your books, we make their ID visible.