To try and simplify it a bit more think of it as switching funds from an account that can only wire to one with a small swipe fee. You have to pay the original wire to wire the funds into the small swipe account, this can be only used with merchants and users that accept the swipe accounts. If you want to send it back to your wire account you need to pay the wire fee again to close your swipe account.
It's a great system for merchant use, the idea is you could pull out a few hundred from your main btc to your lightning wallet use it at stores spend it all up and refill it when needed.
Supermarkets, cinemas, bars, restaurants, etc. I think it's a solution that can be very useful and speed up adoption in the real world, more than in online payments. With Lightning Network it could be possible to make your daily purchases and pay with bitcoin without having to wait for the transaction to be confirmed on the network. Fast and cheap.