Logistics battalions were units attached to the Grand Army of the Republic, which supervised the complex process of bringing reinforcements and equipment to the GARs front-line formations. Along with Fleet Ops, they were constantly kept updated on the status of the military's lines of supply by the Logistics center at Coruscant Command HQ.
Although attached to the clone forces of the GAR, it is not directly indicated in the evidence that the personnel of the Logistics battalions were clone troopers, and they may conceivably have been seconded from the Judicial Department and local militias.