Guys explain me something...
I didn't get it on the end when he says he was comstock and booker
i didn't get it can someone explain to me?
There are constants (there is always a lighthouse in each universe, there is always a man, there is always a baptism) and there are variables (what the lighthouse leads to, who the man journeying to and creating the lighthouse is, if Booker chooses to be baptised or not). In every universe, there is a baptism (assuming Booker isn't dead before then I imagine) and Booker makes a choice. If Booker chooses to be baptised he takes on the name Comstock, and he eventually meets the Luteces. Booker founds Columbia (I imagine that because he was a gambler that he used tears to become rich and then because everybody pays 50% of their income in Columbia to Booker he was able to sustain it [or alternatively that was the source]) and continue to use the tears to see the future (although as far as I'm aware, he doesn't see the entire future). He gains cancer due to exposure from the tears and becomes sterile.
Now we revert back to the baptism. If Booker does not become baptised he is unable to forgive himself and becomes an alcoholic and a gambler, getting himself into significant debt. Sometime within this timeframe he has a child named Anna. To absolve him of his debt he agrees to sell his child to the Luteces. He immediately regrets this and tries to reclaim Anna but is unable to do so, Anna being brought successfully into Columbia.
Back to Comstock, Comstock saw that Columbia would only succeed if his child would sit the throne. After being rendered sterile he was unable to naturally acquire his child and thus resorted to getting his child from another universe. After successfully obtaining Anna/Elizabeth he murders his wife who believes he had an affair with the female Lutece (which, according to a Voxaphone, he asked for but was declined) because she could not promise him silence about Elizabeth's origins, only forgiveness. He then sought to murder the Luteces but his efforts failed and they got trapped within the timeline.
At this point, the Luteces met Booker once more (I believe in the female Lutece's desire to try and reset events as they would have been without their interference; this belief stemming from a Voxaphone) to give him the chance to travel to Columbia and get back Anna. After they brought him to Comstock's universe he created his own memories where he had to "bring us the girl and wipe away the debt". Therefore there is two Booker's in one universe (although, if you want to be technical, there is two Booker's in an infinite amount of universes).
Immediately after, and because of the baptism, in half of the infinite set of universes, in which Booker exists, he is Comstock, choosing to be baptised. In the other half, he is Booker.
the significance of rapture, some are suggesting that its another loop of the same story but i cant buy that. i prefer to just think of it a delightful fan service.
It is, kind of. As Elizabeth says, there are constants and variable. In every universe there is always a lighthouse and a man. It isn't necessarily a loop of the story told in Bioshock Infinite though. So for example, in the set of universes in which Columbia exists, Rapture does not/will not exist and vice versa. Likewise in universes where neither Rapture or Columbia exist, there is another lighthouse with another man journeying to it (or creating it, it's never specified whether the man is the creator or the traveller).
Edit: Although as you say, it's probably there just for fan service but it also helps justify having "Bioshock" in the title.
