ما معنى Quantile regression, mixture density network؟

Quantile regression fits the conditional $\alpha$-quantile by minimising the average pinball loss $\mathcal L_n = \frac1n\sum_i\ell_\alpha(y_i, f_\theta(x_i))$ (Koenker and Bassett, 1978); with several levels it describes the whole distribution. A mixture density network outputs the weights, means and standard deviations of a mixture of $K$ Gaussians and is trained by their negative log-likelihood (Bishop, 1994).