USACO Switching on the Lights

Problems and Contests
#1

In the solution provided by the USACO guide, what does the expression inside the parenthesis do?

vector<vector<vector<pair<int, int>>>> change(MX, vector<vector<pair<int, int>>>(MX, vector<pair<int, int>>()));
#2

It’s the same as method 2 here (but with more dimensions).