This in particular is referring to a lightning node. There are a lot of different ways it can be done but the basic idea is that you are able to use the lightning network in a self-custodial manner instead of relying on a custodian payment service. It involves running a Lightning implementation on your own hardware, and opening and maintaining your own lightning channels for sending and receiving payments. It gives you more flexibility and control, but also more complex and expensive than just using a custodial service. I’d recommend looking at Start9, Umbrel, and Alby Hub to get started.