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C++ Language/Indirection/RvalueReferences/PerfectForwarding
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
If both move-semantics and copy-semantics exist in both a base class and a derived class, then you might need to maintain the choice of move-or-copy when a derived class' function delegates up to the base class' function.
To maintain that move-or-copy choice, std::forward<> is used.
Additional information about perfect forwarding (includes interactive examples)