Hope i get this right because i read about the forks on ethereum days ago and i am not really sure of it.
Whenever a fork happens, it splits one particular blockchain into 2 branches? which means generally they are still under the same chain but it just splitting into A and B? Sorry to ask this because even i took courses in IT but in our country, our education doesn't touch stuffs like cryptocurrency, blockchain perhaps we are still slow.
Yes, 2 branches. Just you will refer to them from that point as 2 blockchains, not as 2 branches.
They have some history together, but no future together. So it's not anymore the same chain.
Same chain would mean that a NEW transaction on one branch would be accepted on the other branch and this doesn't happen.
This is an explanation ... rather confusing.
A theft had happen. So what they did (from what I know) : they did TWO STEPS:
1. They did a rollback to a block just before the theft transaction had happen. This is a "go back into history". The new "NOW" became a point where the theft didn't happen "yet".
2. They did a fork THERE.
The result was a branch (chain) with the correct history and supported by some, a branch where the theft DID happen (ETC)
and a branch with some history erased, where the theft did not happen (ETH).
While the ETC branch is more correct by common sense, the ETH branch is the one supported by the original devs and it has a pretty good reasoning because it stopped a huge theft (although I don't like the approach).