What is "&&" in VoidName( vector

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• What does T&& (double ampersand) mean in C++11? 4 answers

I have recently encountered this code

struct HLD
{
    //typdef vector< vector<long> > dsk;
    dsk ke;
    vector<long> par;
    HLD(dsk &&ke):ke(ke), par(n+1)
    {
        //
    }
};

What is "&&" stand for (i've already know & is taking the address) and what does HLD(dsk &&ke):ke(ke), par(n+1) do ?