Terminator - What is it about

After Terminator 4 came out, many people asked me what the hell is happening and how come Kyle Reese who is so young can be John Connor's father etc. I'm writing this blog post to clear up the confusion and hopefully ignite some interest in the Terminator series, which I feel are very good movies.
Ok, here goes..
Before we proceed, I want you to forget about everything you have seen or know in Terminator. Just let me start explaining from the beginning, and then I will explain in detail.
Terminator 1
- Year 2020+
Mankind are at war with the Machines, and the humans are winning. The humans are lead by, John Connor. The Machines in a desperate attempt to win, build a time machine and send a Terminator, a T-800 (Arnold) back to 1985 to kill John Connor's Mother, Sarah Connor. The humans capture the time machine and send Kyle Reese back to 1985 to protect Sarah Connor.
-Year 1985
In this year, Sarah Connor is not yet married and do not have a son yet. She forges a r/s with Kyle Reese while on the run from the Terminator and as a result, became pregnant. Kyle Reese managed to destroy the Terminator, but died from his injuries.

Terminator 2
- Year 2020+
The Machines send back a more upgrade and modified Terminator (T-1000) to 1995 to kill a 10 year old John Connor. The humans responded by capturing an old Terminator model, T-800 (Arnold), and send it back in time to protect John Connor.
- Year 1995
John Connor and his mother managed to destroy the T-1000, with the help of T-800(Arnold), and also destroyed the company that created the machines, Cyberdyne Corporation. They believed that the future is unwritten yet and they can change the future from happening.

Terminator 3
- Year 2020+
The machines again send back a more upgrade and modified Terminator (The female robot) to 2005 to kill a young John Connor. The humans responded by sending Arnold back in time to protect him.
- Year 2005
Judgement Day happened and John Connor realised that the future cannot be changed. You can only alter the events leading up to it, but there is no escaping the future.

Terminator 4
-Year 2018
Because there is no escaping the future, John Connor knows that in the end the humans will win the war. However, he have to ensure this by making sure that key events happen, such as sending Kyle Reese back in time to protect his mother. The machines also know that they will lose the war, so to prevent this, they are searching for Kyle Reese.
However, John Connor found Marcus Wright, a cyborg that is half human, half machine and begins to lose confidence in the theory that there is no escaping the future and that the humans will win the war.
However, he still sticks to the belief that he has to save Kyle Reese. As a result from his fight from the Terminator (Arnold), his face was cut. This wound can be seen in Terminator 1 and 2.

So, it again confirms the theory that the future is already set, and the humans will win the war.

Terminator Models
T-1: A machine that has wheels as legs. Very dumb and clumsy
T-600: A slow moving Terminator. Has a human endoskeleton.
T-800: A strong Terminator that is massively upgraded. The machines give him human skin, eyes etc so he will be able to blend into the crowd. He can genuinely sweat, bleed and able to impersonate voices. This is Arnold's character.
T-1000: Appear in Terminator 2. Played by Robert Patrick. This Terminator is made of liquid metal and so is able to change forms/shapeshift.
T-X: Appear in Terminator 3. The female robot. Also made out of liquid metal, but this time has weapons from the future built into her. So she can fire lasers etc.

The time-space paradox
The terminator deals with the time-space paradox.
The paradox is simply, say I build a time machine and travel to the past and kill "me in the past". As I will die in the past, I won't be able to build a time machine in the future. And if I can't build a time machine in the future, I won't be able to go back in time and kill me. So I won't die.
This is the time-space paradox.
However, the terminator suggests that major events won't change or be prevented. You can only alter the minor events leading to it.
So, if a person, say Bob, was supposed to die in year 2010, because he got in a car accident when drink driving. He managed to prevent it from happening by not drink driving on that day. But, he will still die from a car accident, for example he gets knocked down instead.

So in the Terminator series, if Kyle Reese failed to save Sarah Connor, another person would still take up the leadership in the future and win the war against the machines.
This is the theory that the Terminator offers.

Timeline
I have made a timeline to explain the events of the story clearer.

Timeline 1: Sarah Connor meets an unknown man and gives birth to John Connor. Judgement Day happens and John Connor becomes the leader of the resistance, leading the humans to victory. The machines send back the Terminator back in time to kill Sarah Connor. The humans send back Kyle Reese to save her.

As a result of this, a new timeline has been formed.
Timeline 2: Instead of Sarah Connor meeting an unknown man, she meets Kyle Reese and gives birth to John Connor. This is why in the future, John Connor is 30+ while Kyle Reese is only 18+, but yet Kyle Reese is John Connor's father.

Ok, the end. Hope it wasn't confusing for you.
I believe that the next terminator movie will show Kyle Reese being send back in time. Possibly the Terminator(in T2) too.
Can't wait for it!