Overall meaning : Warn people, Muhammad, of the approaching Judgement Day and its horrors—when people’s hearts will, out of intense fear, chokingly come up to their throats, making them unable to speak. The wrongdoers will, on that day, have no intimate friend or intercessor to intercede with Allah for them and whose intercession will be accepted.
He is fully aware of the most furtive of people’s glances and whatever secrets their hearts conceal. Allah will judge between people with complete fairness, but the idols that the idolaters call upon besides Allah cannot judge at all. Allah alone hears and sees all things.