There are a few theories out there that could explain déjà-vu, but the most likely one is that it’s simply a glitch in our brain. When we have déjà-vu, it feels like we’re reliving a moment from the past, but in reality, we’re just experiencing a brief moment of confusion. This theory suggests that our brain is trying to piece together memories from the past and present, but for some reason, it gets mixed up and we end up feeling like we’ve already experienced the situation.