You've come to the wrong place for an explanation, but I'll give you a shitty one anyway 😂
It uses your follows and your follows follows etc... to build a Web of Trust map, which it regenerates by default every 4 hours. Based on the level of trust you define, it only allows posts that fall within your defined level. Any posts outside this it rejects. This should pretty much eliminate spam, but it also means that anybody within your defined WoT can write to this relay, but nobody outside of it can.
For me, I hit the limits straight away, which is 40,000 trusted npubs and 1,000 relays. That doesn't mean it included all npubs and relays because of hitting this limit. But I follow a lot of npubs, so it probably doesn't hit those limits for most. I could increase those defaults, but as I'm only running on a $6 VPS, I don't wish to tax it too hard.
I'm still learning, so I'll be posting here as I go.
