As the same gross salary can and will result in very different net payments to the employee, it does not make much sense to discuss salaries in 'net'. In any job description or offer, and in most discussions, salaries mentioned are therefore gross values.
It depends of course of the circumstances - a job that somebody currently has results in a well defined net payment to him, and he might tell his friends his net payments. However, as anyone else in the same position for the same company would probably get a different net payment, the information is not very useful, and a gross salary would actually give more information.
You will never get a job offer or description with a net payment, it does not make sense.