Background on the GeoTools project; and any project specific instructions to help new developers get going.
When writing for the welcome section please consider the target audience as experienced in Java, but not experienced with spatial constructs and ideas. We must focus on results, not correctness.
Here are some examples:
Introduce the concept of a Feature, but not Java Generics.
Show first, explain after - given your target audience showing them the source code first will put them at ease. That way when you are talking about what a Feature means afterwards they will know to pay attention (it is after all a real concept that they must deal with in the form of a Java interface).
Leave the specifications out of it as much as possible. You can link to the specifications as “related information”, and talk about ideas such as ISO Geometry - but do not drive people crazy.
They are here to get a job done - it is your job to understand the specification so they do not have to.
You can create a “Welcome for…” page if you have a different target audience in mind.