I am studying Gaussian mixtures from the book Pattern Recognition and Machine Learning by Chris Bishop. Figure (a) are contours of the mixture components (Gaussians) with the corresponding weights. Figure (c) is the surface graph of the same.
Figure (b) is the 'combination' of the individual components of the mixture. The book labels it as the contour of the marginal probability density of the mixture.
I do not understand why it is 'marginal'. Is it correct to say that 'marginal' is 'combination' of the individual mixtures because that is how is see it. Please provide some insights. Thanks