Value Adding (VA) - these are the activities which add value (actual or perceived) to the product or the service. A value adding step should satisfy one of the following conditions
1. Customer should be willing to pay for it
2. Transformational by nature
3. Done first time right
Waste or Non Value Adding (NVA) - any activity which adds cost or time without adding any value or any activity which does not satisfy any of the above three conditions is a waste or a non-value adding activity in a process. Focus should be in eliminating such activities. E.g. waiting, rework etc.
An application oriented question on the topic along with responses can be seen below. The best answer was provided by Nagraj Bhat on 12th September 2017.