This is a theoretical question. I am a newbie to artificial intelligence and machine learning, and the more I read the more I like this. So far, I have been reading about the evaluation of language models (I am focused on ASR), but I still don't get the concept of the development test sets.
Sometimes we use a particular test set so often that we implicitly tune to its characteristics. We then need a fresh test set that is truly unseen. In such cases, we call the initial test set the development test set or, devset.
In any case, I still don't understand why an additional test has to be used. In other words, why aren't training and test sets enough?