The second ayah is the continuation of the question in ayah 1.
[Translation: About the great news --]
The word naba means news. However, the word khabr, in Arabic, also means news. What's the difference between the two and why is naba used here?
1. Naba is a greater and more important kind of news.
For example, if someone tells you the store closes at 10, that's khabr. But, if someone won the election or there's a war going on or something huge is happening, that's naba. Khabr is used in the Quran twice and both times in the same context: when Musa (a.s.) was with his family in the dark and saw a light in the distance, he tells his family that 'maybe I'll bring you some kind of khabr'. Musa (a.s.) wasn't sure what kind of news he might bring back, if it would be beneficial or not...which brings us to our second point:
2. Naba necessarily has a benefit for the person receiving the news.
For example, when Allah speaks of the nations that were destroyed in the past, naba is used. By listening to stories of past nations, we can learn valuable lessons...which brings us to our third point:
3. Naba is the kind of news that demands a reaction and an action.
For example, if there's a fire in the building, that would be naba – it demands you to take action: to get out of the building, to inform others, to save yourself and whoever else is in the building. When you hear naba, it demands you to change something about yourself.
From this, we can also tell that naba is a manifest event; it's a material and physical event, something that's tangible, something that you can see and touch. When Allah refers to the next life as naba, he is referring to its tangible nature. Other religions sometimes say that the afterlife is spiritual and intangible, that it's a state of mind; however, we learn from this ayah that the next life is very real – in Islam, heaven and hell are real places and not just a state of mind.
So, combining this ayah with the previous one, we can understand that Allah is asking: is it true that they (the disbelievers) are asking one another of this enormous event (the Day of Judgement) in such a sarcastic tone? The news of the Day of Judgement is supposed to lead them to some sort of action but, instead, it is leading them to this kind of ridicule.