The basal ganglia are a group of interconnected subcortical nuclei that represent one of the brain's fundamental processing units. In humans basal ganglia dysfunctions have been associated with numerous debilitating conditions, including Parkinson's disease. To appreciate fully how complicated systems can malfunction, it may first be necessary to understand how such networks work normally. The present review therefore provides an outline of basal ganglia architecture emphasising their interactions with brainstem structures. The potential functions of the basal ganglia network are then considered together along with resulting insights that may help our understanding of Parkinson's disease and other basal ganglia-related disorders.