Computing the distance between each pair of points

[Truman]

X = rand.rand(10, 2)
%matplotlib inline
import matplotlib.pyplot as plt
import seaborn; seaborn.set() # Plot styling
plt.scatter(X[:, 0], X[:, 1], s=100);
dist_sq = np.sum((X[:, np.newaxis, :] - X[np.newaxis, :, :]) ** 2, axis=-1)

what I don't undersand is this part:

differences = X[:, np.newaxis, :] - X[np.newaxis, :, :]

what's happening between these two brackets, these two colons. Help is appreciated.