Looking for doco: TransactionObj , also "Category"

Hi, two things I’m looking for info on but haven’t found answers in the book, wiki, perldoc, and only scratchings on the mailing list.

In scrips, what is the set of values that can be returned from TransactionObj->Type ?

From looking at hundreds of emails I seem to have gleened that there is at least ‘Set’, ‘Resolved’, ‘Status’ and ‘CustomField’.
What else?
I’m confused by ‘Status’ and ‘CustomField’ as I would have thought changing those things would be Type ‘Set’.

"select" Custom Fields have a column marked “Category” in their values section.
What does this do?

Let me know and I’ll put some documentation on the wiki.