This page introduces all the different way of explaining the idea.
Social Contract
I don´t really use this analogy very often as it is a bit too philosophical and not so useful, but I´m including it here for completeness. The idea can be thought of as an improvement on the standard idea of a social contract. The social contract is usually thought of a fixed single agreement that is the same for all members of society that covers all aspects of life. In the proposed idea all these aspects are divided up into individual contracts that people can freely sign up to (by how the set up their filters). So I suppose it can be considered to be a continuous (rather than discrete) social contract, with infinitely many clauses that each individual can sign up to depending on their own ethics.
Village analogy.
Explained on the Village analogy page. Basically an analogy that imagines how a very small society would work if it had not created the idea of money, but instead the citizens remember what everyone else has done for that small society and use this information to decide how much to assist other individuals. This analogy I do find useful as it helps me solve practical and ethical problems with applying the idea at larger scales.
Filtered reputation systems.
Already explained this on the home page. Simple but not really thorough enough.