It innervates the 3 salivary glands in the mouth. The saliva from these glands mixes with the chewed up food to form a bolus. Also, along with the vagus (CN. X), it provides some innervation to the upper pharyngeal constrictor muscles.
It helps to elevate the larynx and pulls it forward during the pharyngeal stage of the swallow. This action also aids in the relaxation and opening of the cricopharyngeus muscle.
The glossopharyngeal nerve mediates all sensation, including taste, from the posterior 1/3 of the tongue.
CN. IX also carries sensation from the velum and the superior portion of the pharynx.