Ok honestly speaking i dont think someone can understand it for the first time. You have to watch it twice for sure. The first experience of it was like i was sitting and cant understand whats happening. And at last i knew everything but couldn't understand anything but a bit upto the half. The second time it was like i knew everything, so i started connecting them. Each scene with the story i started understanding.
The movie is all about stopping the war between the future and past. The future wants to destroy the past so there would be no future. And our hero, the protagonist has to stop it. Its not like time travel,but reversal of time, normal objects go forward with the time but the inverted ones travel backward with time. And if the whole world gets inverted,it would be the world war 3,the end of this world.
Even after watching it twice i still have some doubts in my mind. (I need mr Nolan's number so i could clear them😜 ). You can't get it out from your head for days.
WHATS HAPPENED IS HAPPENED