I thought its not so confusing when it goes like this: The first three Terminator movies actually have a pretty solid timeline, if you look at it as a whole. Forget about the fourth Terminator film, partially because your brain cells will thank you, but mainly because it doesn’t figure into this. We’ll also ignore the fact that Skynet is the stupidest sentient AI in history. (Why would you send your most powerful Terminator back to the time when he’s a freaking adult? Send it when he’s a kid, for God’s sake.) John Connor sends his own dad back in time to keep him safe as a kid, then two T-800s, one to his early teen years and one to his early 20s. Kyle Reese successfully keeps him alive. Cool, timeline preserved. But then in Terminator 2, they prevent Judgement Day. Wait a second here. If you prevented Judgement Day, you negated the reason for sending Kyle Reese back in time and therefore John Connor doesn’t exist. But technically, the Terminator from the first movie doesn’t exist either, so there’s none of his leftover bits to reverse engineer to create Skynet either, right? Except that the third film establishes that Skynet was going to come online anyway because the military bought up Cyberdyne, and so they’re the ones built Skynet in the first place. Luckily, it also re-establishes that Judgement Day did occur. So, really, the timeline is still intact, but Skynet is also still really fucking stupid. The trilogy T4-6 follows the events after Judgement day to complete the cycle. Although 5&6 seem to be living in development hell
My my my, I don't think I have ever seen T1, T2, or any other terminator for that matter. Wow. I'm gonna look it up and give it a go.