The network creates a second layer on top of the bitcoin blockchain and comprises user-generated channels. You can securely send payments back and forth without the need to trust or even know your counterparty.
Say, for instance, that I wanted to pay you for each minute of video that I watched. We would open up a lightning channel, and as the minutes rolled by, periodic payments would be made from my wallet to yours. When I’m done watching, we would close the channel to settle the net amount on the bitcoin blockchain.