Naming

Interfaces are named in the same way as classes - LikeThis.

In the wild west of the real world you might see people prefix any interface name with I, for interface.

In these cases instead of Dog you would see IDog. Instead of PartyAnimal you would see IPartyAnimal and so on.

The reason someone might do this is if they think it is worthwhile to have a visual indicator of whether a type represents an interface or an actual class. Personally, I don't think that is too useful, but there is nothing horrible about it.

Just judge the social context you are in and don't hold it against people too hard if they do it a way you don't like.