Lightning Network is a payment protocol that operates on top of the blockchain.
In the Lightning Network, operations do not require confirmation of blocks; they are carried out using payment channels between specific nodes. Thus, you can make a lot of transactions, and then write them into the blockchain as one — this increases the speed of transactions and reduces commissions.
Therefore, buying coffee for Bitcoins or Litecoins will soon become a reality (these two projects are already integrating the Lightning network), because you will not have to wait an eternity until the payment is processed. For comparison: the Bitcoin network previously performed seven operations per second, together with Lightning, this figure could potentially grow hundreds of thousands of times.
When this issue is finally resolved, the cryptocurrency can safely compete with such payment systems as Visa, MasterCard, and PayPal.