C++: What is the difference between std::deque and std::queue?

1// deque — double-ended queue
2std::deque<int> dq;
3dq.push_front(1);
4dq.push_back(2);
5dq[0];  // Random access
6
7// queue — FIFO adapter
8std::queue<int> q;
9q.push(1);
10q.push(2);
11q.front();  // 1
12// q[0];  // Error!