What does the "template" keyword mean when places after scope resolution operator (::) [duplicate]

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• What does ::template mean other than making TMP compile [duplicate] 2 answers

I came accross the following construct while reading this article:

template<typename F, typename...As>
using meta_apply = typename F::template apply<As...>;

Can someone explain to me what does the template keyword mean when it's placed after the scope resolution operator ::? Or better point me to where this usage is described in C++ reference of any kind. I tried looking it up myself but couldn't find any.