This is the "killer feature." When you open a source file, the XRef engine hyperlinks every function, variable, and type. If you are looking at Context.java and see a method call to getSystemService() , you can click that method name. The tool will instantly show you a list of everywhere that method is defined or overridden. This allows for "spelunking"—diving deeper and deeper into the code hierarchy without losing your place.
When you perform a search, you aren't searching the code files directly; you are searching that index. This allows for advanced query types: xref aosp
Xref AOSP scans the entire AOSP repository, builds a full index of symbols (functions, classes, variables, macros), and presents them through a web interface. It understands: This is the "killer feature