Micropayments channels bitcoin uses to scale its blockchain capacity to conduct transactions which acts as a second layer technology on its network is known as lightning network.It was featured first in 2016 and today, it's being implemented.
The function of lightning network is to ease congestion on bitcoin network, increasing the transaction speed while doing these not specifically on bitcoin network. It performs these function away from bitcoin network to make the daily usage and access to bitcoin easy and possibly makes it go mainstream.
It also makes possible to exchanging of one cryptocurrency to another without the need of intermediary and this is known as atomic swaps.