The Patrol Division is historically referred to as the "backbone" of the police department, and is responsible for patrolling the city 24 hours a day/7 days a week.
Officers of the Patrol Division are typically the first responders to any dispatched or self-initiated incidents. As an example they are:
the first responders to domestic disturbances, thefts, burglaries, robberies, etc.
deal with a host of high-stress situations and crimes
perform traffic stops and investigate traffic accidents
All new police officers are assigned to the Patrol Division for their field training and introduction phase to law enforcement. These officers then either choose to stay in Patrol or take their knowledge and experience into other divisions.