Can someone explain it to me? I heard that the transaction speed would be much more faster, but I don't know how it works
It is very complex and it doesn't have a user-friendly interfacing feature quite yet.
If you really want to learn about it, start from standard features such as multisig. Then read up on state channels. And then you'll start to get a grasp.
Alternatively you can wait a relatively long time for LN to be in a more finished state, and use it without understanding its internals. But we're plenty of years away from that.