From W3C Wiki
A SlashURI is a URI without a hash mark ("#") in it (technically, a URI without a fragment identifier), especially one used in RDF to denote something which cannot be viewed in a browser. This term is in contrast to HashURI; both are ways of handling the situation when WhenBrowsableAndUnambiguousCollide. The terms sound nice together as HashVsSlash.
SlashURIs look like
How does a SlashURI handle the collision of Browsable and Unambiguous?
Sometimes it's ignored. The "collision" only manifests when you actually want to talk, for instance, about both a chair and about a web page about the chair. Some people think such multi-level expressions will become more common as semantic web agents need to reason about where to find information about things, ... but the actual problems have been minor so far.
Sometimes it's done with SlashRedirection.
The question of what SlashURIs denote is tag:httpRange-14 and touched on in ResponsePoint.