"Oh! I'm so definitely sure that I've lived this situation before" - And that my friends is what we call Deja vu. Everyone has been to this situation, I've been many times. There is indeed one way to explain how Deja vu occurs. Or basically we can say that there are 3.... First is that the time-space continuum had an instant glitch, second is that something in the Matrix has changed, and third is the explanation that i put my money on.
It seems that there are many "stops" for the visual signals before they end up to he back of your brain which is the place where visual information is decoded. This has been proved also by a weird phenomenon that happens to people with blindness caused by brain damage. Although these people are blind, they may unconsciously react to certain stimulation like a person's face or blocks in their path. This may also explain Deja vu. You may feel that you've seen something before, only because you saw it before and you just did not decode it immediately, or your brain reseeds this info to the optical decoding center for a second time!
Watch this following video to learn more about Deja vu, Presque Vu, Jamais Vu and the all-famous Hypnagogic jerk!