C++ Need help to understanding syntax of a parameter passed to a function vector<vector<int>> A[]

I am solving a question where a function is defined as following:

vector <int> func(int a, vector<vector<int>> B[]){
    // Some stuff
}

I am confused about why the second parameter is not only vector<vector> B why the extra [] part in the parameter. Can someone clarify the meaning of this parameter vector<vector> B[]?

The vector B is populated by a similar code snippet:

vector<vector<int>> B[10]; 
while(num--){
    cin>>u>>v>>w;
    vector<int> t1,t2;
    t1.push_back(v);
    t1.push_back(w);
    B[u].push_back(t1);
    t2.push_back(u);
    t2.push_back(w);
    B[v].push_back(t2);
}

>Solution :

B ist a static array (C-style) of 10 elements [0 .. 9]. It’s not safe and this code is a terrible mess.
Better use std::array<std::vector<str::vector<int>>, 10> B; instead to have index checking.