On load a pre-calculated neural network is provided and you can try that immediately. You are supposed to draw numbers on drawing area and then network tries to figure out the number. The number is given neural network as pixels and neural network outputs the likehoods how well the figure match with each digit. The histogram and the best likehood gives you idea how sure the network is about its conclusion.
The verify button calculates independent test material over the network to give an objective and comparative value of network match accuracy.