Why `std::unordered_set<std::vector<int>>` does not compile whereas `std::unordered_set<int>` is ok?

Here is the code snippet.

Why std::unordered_set<std::vector<int>> does not compile whereas std::unordered_set<int> is ok? Could someone please give me a detailed explanation?

UPDATE: Here is the error messages:

error: use of deleted function 'std::unordered_set<_Value, _Hash, _Pred, _Alloc>::unordered_set() [with _Value = std::vector<int>; _Hash = std::hash<std::vector<int> >; _Pred = std::equal_to<std::vector<int> >; _Alloc = std::allocator<std::vector<int> >]'
    ...

Tips: Sorry, I can't fully understand the error message.

  #include <vector>
  #include <algorithm> 
  #include <unordered_set>
  #include <iostream>
  #include <vector>
  
  int main()
  {
    std::unordered_set<std::vector<int>> set_of_vector;  //Why this one goes wrong?

    std::unordered_set<int> set_of_int;

    return 0;                    
  }