The concept of it is for better and fast transaction in the network, during the end of 2017 and 2018 the network fee's are expensive for transfering and the network sometimes take times i experience it first hand
almost takes me a day for a transfer, and at the same time the fee's are so high, here is a link to better explain what really lightning network and some explanations
https://news.bitcoin.com/heres-what-happens-when-you-use-lightning-network-for-the-first-time/
for better understanding