I've seen NLU and NLG described as areas within NLP. I think generating headlines from an article would use a bit of both. A pure NLG task would be more like c

I've seen NLU and NLG described as areas within NLP. I think generating headlines from an article would use a bit of both. A pure NLG task would be more like creating sentences to describe the weather based on weather data, or medical data on a patient, etc. I'm not an expert in the field though, really just a beginner so my understanding may be off.