Lightning network is made up of payment channels that can route to each other if there is enough liquidity balanced in the channels.

To open a Lightning channel with a someone requires paying a L1 bitcoin fee.

Basically it works like bar tab. Instead of paying the L1 fee every time you make a payment. You only need to pay the L1 fee once to enable payments.

It gets pretty complex when you start talking about LSPs and node runners though.

So that’s why custodial wallets like Wallet of Satoshi are very popular as it removes all the complexity but you instead of to trust a custodian with your funds.