Erm... The original release had a talk over at the start explaining things. It ruins the film once you know it, so the director's cut is better, but it's much more confusing.
The replicants are genetically created people. With the genetic code designed to make them stronger and smarter. However, they are released fully grown and programmed to do their jobs.
To function well, then need the intelligence, but this led to them realising they're better than humans and being treated as slaves. So they rebelled. This led to replicants being banned from Earth, and that they all had to have a shortened life span. So their age (based on inset date) is hard coded into their genes. It's supposed to mean that they never live long enough to get curious and work out what they are, and that they should fight it.
The four in the film are all highly developed versions, part of a new wave that had been put out which are even better. That's how they made it to Earth.
Harrison Ford (Deckard) is a Blade Runner - a replicant bounty hunter working for the police. Only at the start of the film, he's retired. He's re-hired to find the four who have come to Earth.
At the start, you see the test to see if someone is a replicant or not - the test works on emotional response - replicants don't know how to handle emotions, as they are not programmed with them, and they can't develop them as they only live a couple of years. Imagine the emotional responses of a two or three year old - they haven't lived long enough to understand how to deal with love, hate, frustration, etc. So they lash out. Replicants are emotionally at the same level, only massively more intelligent.
The latest models have false memories implanted, so they don't even know they're a replicant. As they have memories, they can relate emotional responses back to times in their life which were important for them to grow. They obsess over those memories though, stories, photos, music, dreams, etc. It all helps the replicant come to terms with their emotions. So you have the complication of Rachael in this situation - someone Deckard by law should kill!
So the film is all about the replicants searching for meaning, and to understand themselves, and why they feel the way they do. They also want to know if they can be 'made' to live longer. It's a quest for God and understanding.
The film is on many levels, so you have multiple stories running simultaneously, which is what makes it so rewatchable. The first time you may just see it as a sci-fi cop action film, but the next time you see it from the replicant's view as the search for knowledge, the next time... Well, it's up to you to watch it and get more from the film
Taylor would hate it! :lol: