[travoltaj]

Two things - First - I learn how the data flows from the source to the end. That teaches me to navigate the codebase entirely. (User action to database, or source data to end data etc.

Second - I learn how different components are wired together.

[jarusll]

So indexing all the components and finding out all the interactions between them. This is exactly what class browsers do, they index all the classes and messages. The interactions could be described using an example/documentation.

This reminds me of Pharo which does all of the above, indexes classes, messages and has a rich documentation support.