Have you ever had a premonition?
A premonition is most simply defined as a strong feeling that something (often unpleasant) is going to happen in the (typically near) future.
These are generally feelings that most often strike when a person is awake but with no real specific knowledge of what the event to pass is.
Precognition is slightly different but often thrown into the same basket. However, precognition is more like a true future sight – often taking place when one is asleep or in a dazed / relaxed state – and along with feelings of imminent urgency these are usually accompanied with visions and sounds; a more clear picture of the event itself.
However, often, but not always, in both cases the person having these sensations / sights will not have all the specifics needed in order to really nail down the what, why, who, where and when of the event that is to take place.