Minecraft wiki entry for Tick, associated text: In Java Edition, there are two types of scheduled ticks: block ticks and fluid ticks. Block ticks are executed first based on priority, and then based on scheduling order. A lower value for priority results in earlier execution during the scheduled tick phase. If a redstone repeater is facing the back or side of another diode, its block tick will have a priority of -3. If a redstone repeater is depowering, it will have a priority of -2. Otherwise, the repeater will have a priority of -1. If a redstone comparator is facing the back or side of another diode, it will have a priority of -1. All other block ticks will have a priority of 0. Then, each block with a scheduled fluid tick will tick. Fluid ticks do not use priorities and are only ordered based on scheduling order.