i believe that they stand for (Non)Deterministic Finite Automata.
There is a seemingly complete description here:
Powerset construction - Wikipedia, the free encyclopedia
since you're asking the question you're probably in a course which allows you to be much more familiar with the topic than me.
from reading the wikipedia page above I think I understand the algorithm enough to help you work through it but you're going to have to do your part as Nosnosna said above.