Wot is web of trust. It's like a digital map of your friends and their friends and their friends and so on. The friends of your friend are ranked higher as they're less likely to be spam or scammers versus someone say 5 levels away from you. You can think of it like 7 levels of Kevin bacon. You trust more the ones closest to you. Relays and clients can use this social map to help filter out spam and scams.