Inevitably when sequels to popular movies come out, there are people who see the new movie that have not seen the previous ones in the series.

One of the most vital aspects in the "Terminator" story is time travel, which is a plot device present in all of the films. When introducing a complicated concept like time travel though, things can get confusing for viewers because of alternate timelines and time paradoxes.

If you haven't seen any of the "Terminator" movies but you want to see the new one, these ideas might sound complex to you.

Have no fear. I have come up with a cheat sheet for you. After reading my article, you can go into "Terminator Salvation" understanding the timeline of events leading up to it.

*Sorry "Sarah Connor Chronicles" fans, for "Terminator" purists, the show is not part of the timeline or even necessary to understanding the events of the films, so I will be leaving it out.*

"TERMINATOR" ESSENTIAL BACK-STORY

The "Terminator" series is about the human fight against Skynet and the Terminators. Skynet is a supercomputer built by humans, which becomes self-aware and decides to exterminate the human race by manufacturing killer robots called Terminators.

At the center of the series is John Connor, the man who leads mankind to defeat the machines in the distant future. In a last ditch effort to prevent this from happening, Skynet sends a series of Terminators back in time, in attempts to kill John at various points in his life.

These attempts on his life are thwarted by guardians sent back in time to protect him, and John Connor grows up to lead the fight against Skynet. This is where "Terminator: Salvation" picks up, when John Connor is the commander of the resistance in the year 2018.

To get you safely to the year 2018, and to help you fully understand the back-story, I will break down the previous three movies and their timelines.

"TERMINATOR"
In the year 2029, Skynet sends a Terminator model T-800 back in time to 1984. The Terminator's mission is to kill John's mother, Sarah Connor, before he is born.

John's loyal soldier Kyle Reese follows the Terminator back 1984 to protect Sarah. Kyle meets her and falls in love with her, becoming John's father. He protects Sarah and destroys the Terminator but dies in the process.

Through a time paradox, it becomes Kyle Reese's destiny to fight alongside John in the future, and travel back in time to become John's father. Without Kyle's time travel, John wouldn't be conceived and born in 1985.

In addition, the Terminator is destroyed in a factory owned by the company Cyberdyne. The company covers up that the Terminator was there, stealing the Terminator's processor and researching it to build more advanced computers. Cyberdyne goes on to build Skynet in 1997, causing Judgment Day: the day the computer becomes self-aware and starts warfare with human beings.

"TERMINATOR 2: JUDGMENT DAY"

Skynet also sends a Terminator model T-1000 from the year 2029 to the year 1995. This more highly developed and dangerous prototype's mission is to strike at John when he is 10 years old and kill him.

Instead of sending another human back in time, John dispatches a reprogrammed model T-800 Terminator to 1995 back to protect his younger self. The T-800 helps John rescue Sarah from a mental institution before the T-1000 can replicate her form and kill her.

John, Sarah, and the T-800 find the man at Cyberdyne responsible for the construction of Skynet, Miles Dyson, and tell him of his role in the world's bleak future. Miles, Sarah, John, and the T-800 successfully blow up the Cyberdyne offices and steal back the parts from the original Terminator, but Miles dies helping them.

Image © Lions Gate Entertainment

After the T-1000 chases them to a steel mill, the T-800 defeats it, saving John and Sarah's lives. To help prevent further use of the old Terminator parts, or its own, the T-800 tells John and Sarah to lower him into hot iron ore, so that he will be melted down and destroyed.

By blowing up Cyberdyne and destroying the parts the company was using to build advanced computers, John and Sarah alter the original timeline of history and prevent Judgment Day from happening in 1997. Sarah dies of cancer that same year, and John is left on his own.

"TERMINATOR 3: RISE OF THE MACHINES"

John Connor is killed by a Terminator model T-850 in the year 2032. That year, Skynet sends a Terminator model T-X to the year 2004, with the plan to assassinate John Connor's lieutenants, and to prevent the group from forming. One the people on the hit list is John Connor's future wife Kathrine Brewster.

Kathrine reprograms the T-850 that kills John in 2032 and sends to back to 2004, to protect her and John from the T-X.

In 2004, John and Kathrine run into each other after John has a motorcycle accident and uses her veterinary clinic for pain medication.

The last time John and Kathrine saw each other was in 1995, when they met as kids. "T3" makes a factual error and says that that John was 13 at the time, but if he was born in 1985, he would have been 10 years old in 1995.

John and Kathrine meet up with the T-850, and he tells them that Judgment Day will still happen because the Air Force took over Cyberdyne, and developed Skynet. At the same time, a mysterious computer virus begins crippling civilian and military communication networks.

John and Kathrine try to plead with Kathrine's father General Brewster, who is in charge of the Skynet project, not to turn on the computer. It's discovered that Skynet has been the virus the whole time, because it became self-aware and wanted to take out communications so it could strike easier against humans.

The T-850 escorts John and Kathrine to a place called Crystal Peak, where they believe the system core to Skynet is located, in an attempt to shut it down. The T-850 sacrifices himself to destroy the T-X and save their lives. John and Kathrine discover the core is not there, but rather their fate is to survive Judgment Day there to command the resistance.

Hopefully you're finishing this article less confused than you started, and you have a better grasp on the story of the "Terminator" franchise. I'm excited to see "Terminator: Salvation" and what elements it will add to the overarching story of the series.

Story by Starpulse contributing writer Evan Crean, a movie trivia guru and trailer addict with a practically photographic memory of actors and directors. Get a first look at the movies premiering each week, which which ones will be worth your $10, which ones you should wait to rent and which ones aren't worth your time.