WebID is a replacement for traditional login on the Web. WebID is an open standard for identity and login. With WebID you no longer need to remember usernames or passwords for all of the sites you use. You can publish your identity wherever you want and choose what pieces of your personal information that you want to share with websites. WebID is compatible with OpenID, but is much more extensible. With WebID, logging into a website is as simple as selecting a WebID and clicking "log in".
WebID Profile Document#A WebID is an HTTP URI which refers to an Entity (Person, Organization, Group, Device, etc.). A description of the WebID can be found in the Profile Document, a type of web page that any Social Network user is familiar with.
WebID Profile Document is a Web resource that must be available as text/turtle turtle, but may be available in other RDF serialization formats (e.g. RDFA-CORE) if requested through content negotiation.
WebIDs can be used to build a Web of Trust using vocabularies such as FOAF by allowing people to link together their profiles in a public or protected manner. Such a web of trust can then be used by a Service to make authorization decisions, by allowing access to resource depending on the properties of an agent, such that he/she is known by some relevant people, works at a given company, is a family member, is part of some group, etc..