What is the scheme-specific part in a URI?

Each URI begins with a scheme name that refers to a specification for assigning identifiers within that scheme. As such, the URI syntax is a federated and extensible naming system wherein each scheme's specification may further restrict the syntax and semantics of identifiers using that scheme.

See this section of the URI rfc https://www.rfc-editor.org/rfc/rfc3986#section-3.1

From wikipedia :

All URIs and absolute URI references are formed with a scheme name, followed by a colon character (":"), and the remainder of the URI called (in the outdated RFCs 1738 and 2396, but not the current STD 66/RFC 3986) the scheme-specific part.

The scheme-specific-part is what you have after the :.

Example :

    http://stackoverflow.com/questions/24077453/
scheme  :   scheme-specific-part