I have a question otber than atomic swaps what does SegWit open the door for, and what is meant when people say "Layer2"?
I think one of the major "doors" segwit opens is the possibility to develop and implement the lightning network, where tx don't need to be inserted into the blocks. They go there eventually, but only the "final version" of the transaction goes there. I don't know the exact details, but basically a payment channel is created off-chain (and this is the layer 2, because it's outside the blockchain), transactions are recorded in these channels, and eventually a final version is broadcasted into the blocks, and gets stored into the blockchain.
This is great, because you can solve the bitcoin scaling problems without increasing the block size, and this is the best option for the long term.
