Cycle Time in Scrum refers to the time it takes for a Product Backlog Item or a task to be completed from the moment work starts on it until it's considered done. It provides valuable insights into the Scrum team's efficiency in delivering work items. A shorter cycle time generally indicates better efficiency and faster delivery.
A shorter cycle time means the team is working more swiftly and getting things done quickly, while a longer cycle time might indicate potential bottlenecks or areas for improvement.
Slicing the PBIs thinner usually helps keep the Cycle Time low. If your team is consistently able to sliced the PBIs to a point where most PBIs can be completed within a day, in such cases there would be usually no benefit of measuring Cycle Time.