The terms listed here might have a formal defenition, or several, but this list are my take on them. They are described from my perspective as an Agile Coach. Sometimes the term normally used is replaced with an alternative that creates an association that is more useful.
Expected items referred to as beeing expected are those that is part of a forecast and that the stakeholders expect to be completed accordingly.
Items refered to as beeing uncertain are those that is part of a forecast and that the stakeholders can not expect to be completed accordingly.