C++ Class Constructor function

Question

I don't understand the meaning behind this code. Please help me thanks!

template <class T>
Queue<T>::Queue(int queueCapacity) : capacity (queueCapacity)
{ if (capacity<1)throw "Queue is empty";
queue= new T [capacity];
front=rear=0;
} 

i wonder what's the meaning of :capacity (queueCapacity) in

Queue<T>::Queue(int queueCapacity) : capacity (queueCapacity)