A handle can be anything from an integer index to a pointer to a resource in kernel space. The idea is that they provide an abstraction of a resource, so you don't need to know much about the resource itself to use it.
For instance, the HWND in the Win32 API is a handle for a Window. By itself it's useless: you can't glean any information from it. But pass it to the right API functions, and you can perform a wealth of different tricks with it. Internally you can think of the HWND as just an index into the GUI's table of windows (which may not necessarily be how it's implemented, but it makes the magic make sense).
“给你杯子的把手，你就可以去拿它了”
(Give you the handle of a variable, then you can access it's content.)
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