I've never known a concept as deja Vu exist. It means
the strange feeling that in some way you have already experienced what is happening now.
I've had this feeling so many times, at some point I felt I was blessed with the gift of seeing a thing happen before it does in the physical, until recently when I read an article of a writer who experiences the same thing. I do not know the science or mystery behind this feeling, but I believe it's a process that helps us connect with our subconscious mind. This feeling was common with me when I was younger.
I can't remember many of these experiences but there are two events that cling to my memory when the subject of deja Vu is discussed. I visited a family one fateful day and we all engaged in a conversation when a call came in informing the mother of the house about her cousin who had been admitted. The once lively atmosphere became dull, everyone confused as they went Helter skelter trying to get dressed. The event seemed to have happened before, like I've seen this happen, the same place, the same people, and this same peaceful atmosphere disrupted by a call, I just couldn't remember where and when I saw it but it looked as if it was a repetition of what I've seen before.
The second experience happened while I was in school. To my surprise, I had a retake for a course I knew very well. The day I went to sit for the exam, the event that took place while I was seated in the hall seemed familiar. It was as if I'd seen myself in that hall before sitting for the same examination. Like it had happened just yesterday and that day was a repetition of yesterday. There are several times I've had that feeling/experience but it's been a while to recur them all. Sometimes I feel we indeed might have seen these events but it comes in a flash for our mind to capture until it happens.