An anonymity set refers to a group of people or entities that share some characteristic that makes them indistinguishable from one another. For example, users who access a website using a VPN service make up an anonymity set.

A small anonymity set is a group of people or entities that share a very specific characteristic, making it easier to identify them individually. For instance, a group of people who all live on the same street and use the same VPN service would form a small anonymity set. This would be relatively easy to identify and track.

A large anonymity set, on the other hand, is a group of people or entities that share a broad characteristic that is difficult to use to identify any individual. For example, a group of people from all over the world who use different VPN services would constitute a large anonymity set. It would be much harder to track down any individual from such a large pool of users