I dont know about you, but in my case, it is bad memory. Having the feeling that I've been here or done this before is often because I have and dont remember details anymore.

it is a french word, it means something you have seen before

Deja Vu is the experience of feeling sure that one has witnessed or experienced a new situation previously.

You also have Jamais vu which is used to describe any familiar situation which is not recognized by the observer like when a person momentarily does not recognize a word, person, or place that they already know.

And Presque vu is the sensation of being on the brink of an epiphany. Often very disorienting and distracting, presque vu rarely leads to an actual breakthrough. Frequently, one experiencing presque vu will say that they have something "on the tip of their tongue."

Yes that's all very well but WHAT IS IT? How do you explain it? Is it real? Is it possible?

It's a glitch in The Matrix, of course. ;)

I feel Deja vu is a sequence of actions that have happened to me for real or in a dream before.

hey.
i read sumwer that sum scientists explain it this way.
um. your senses for example, your right eye transfer that info to ur mind faster thn your left eye. maybe just a fraction of a second faster thn the other, creating a sense of familiarity, wen there neednt be one.so.
i duno. wadya think?
hope it helps.