Video - Bitcoin Q and A The Lightning Network and Rootstock
The Lightning Network is an overlay layer-two network which uses actual bitcoin transactions to create promises that can be redeemed/ settled on the Bitcoin network in the future, or extended forward in time across multiple participants. This allows you to encompass a much larger volume of transactions, much more fine-grained in time and amount.
You can do millions of participants, millions of transactions, milliseconds apart, for a few satoshis and still make it work by only settling the final reconciliation. It is Bitcoin - Layer 2, or the second layer of any other blockchain that supports the basic multi-signature, timelock transactions, and some basic scripting capabilities.
It adds a dimension of processing that will blow away everything we've seen before. Imagine streaming your salary not every two weeks but every minute, because why not get paid incrementally every minute? Streaming money is the new concept.
Rootstock is an attempt to implement an Ethereum virtual machine on top of Bitcoin. It hasn't been implemented yet partly because it depends on a couple of underlying technologies like Segregated Witness and it needs some new scripting opcodes as well as the ability to soft-fork upgrade some of the scripting language.