mostly if think about this one over here mixture models allows to have them wider range of the situations and their components for example mixture of Gauss is much richer than a single Gaussian for example a single Gaussian all I can do is look like this but a niche model could have many of these bump mix together and then the overall thing would look something like that which is much more complexed representation that you can capture with this five component mixture that with a single gaussian the key question we want to answer is if P