What is the difference between a task and a PBI?

A PBI represents the "what" - it is a high-level requirement or feature that needs to be built to deliver value to the customer. A PBI is typically written from the perspective of the end-user, focusing on their needs and goals. 

In contrast, a task represents the "how" - it is a specific, granular piece of work that needs to be completed to implement a PBI. Tasks break down the work required to complete a PBI into actionable steps.