Not An Answer (NAA) means that the "answer" does not answer the question, and is not actually an answer.
Very Low Quality (VLQ) means that the answer attempts to answer the question, but it is so deficient as to make its value to the site negative, and worthy of deletion.
Depending on the severity, I might delete them in either case.
If it was a Very Low Quality answer, I would see if they had been told to improve the answer, if they had, and been given sufficient time (a week?) but had not, I would delete it.