I can't find any explanation as to what exactly the "scheme-specific part" of a URI is.
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are formed with a scheme name, followed by a colon character (":"), and the remainder of the URI called (in the outdated RFCs 1738 and 2396, but not the current STD 66/RFC 3986) the scheme-specific part.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