I recently read a whitepaper on what seems to describe an implementation of Lightning Network on top of the Bitcoin Blockchain.

https://lightning.network/lightning-network-paper.pdf

Going over the technical details and descriptions of LN, there are many things that I do not get:

1.) What exactly does the LN transx accomplish that a general transx fails to do?
2.) ELI5 the mechanics of LN and the transx that occur. How is the transaction validated onto the blockchain after coins are moved?
3.) What are channels? How does one "open/close" one? Can you create one?
4.) What incentives are there for miners/nodes on the network?
5.) Is there simply a single LN, or can there be several networks running concurrently alongside the blockchain?
6.) What is the bridge between LN and applications running alongside the blockchain?