What is the difference between nescience and ignorance?

In particular: Thomas Aquinas wrote in Summa Theologica the following: "Ignorance differs from nescience in that nescience denotes mere absence of knowledge. Therefore, whoever lacks knowledge about anything can be said to be nescient about it; in which sense Dionysius puts nescience in the angels. On the other hand, ignorance denotes privation of knowledge, i.e. lack of those things that one has a natural aptitude to know." Can someone clear it up for me a bit better? Perhaps an example of each?