system
Given the following post, respond as if you're commenting on Reddit:
human
[MCU] Questions about variants, timelines, dimensions, and multiverses.

Okay there’s gonna be a lot of questions in this one. 

What’s the difference between timelines, dimensions and multiverses. Like how are the timelines they mention in Loki different from the timelines created in time travel in endgame and from the dimensions in doctor strange, and the multiverses in No Way Home and Multiverse of Madness?

How are variant timelines created? Like at a decision point do two separate versions of the person and world get created? How do they decide what a decision point to create a variant timeline is?

What exactly is the sacred timeline and is that a separate thing from the multiverses?

Were the different multiverses created only when Loki and Sylvia killed He Who Remains? And if yes, did those multiverses come into reality fully fledged, like was Peter 1 already at his point past spider man 3?

When the Avengers time traveled in Endgame and altered the past, they say it created a new timeline. How does this relate to the variant timelines in Loki and the multiverses/dimensions? And how are they able to revisit those timelines?
gpt
The timelines created in Loki are no different than the time travel shenanigans in Endgame, except according to the TVA, the Avengers were *supposed* to do that.  Basically in that version of Kang's history, the Avengers traveled through time to stop Thanos.  So he made sure that what they did was okay.  But otherwise there's no real distinction.

Apparently really small changes (like what somebody had for breakfast one day) aren't significant enough to cause a branched timeline.  But there's debate about that.

The sacred timeline is the one that leads to the creation of that particular Kang who they met at the end of Loki.  There's nothing sacred about it except that he's in charge, and he wants to stay in charge, and doesn't want other Kangs appearing.

The Multiverse is different.  The Multiverse takes into account all different possibilities, including ones that are completely different.  There's no amount of time travel you can do that results in a universe made out of paint, or one where we're all cartoon characters.

The Multiverse goes well beyond the scope of anything Kang can control.  It existed before the events of Loki (it was mentioned in the original Dr Strange movie).  In a sense, Kang and the TVA were fooling themselves thinking they had control of all reality.