Final answer:
Scrum Teams use Story Points as an abstract unit of measure for estimating effort required to implement Product Backlog items, based on complexity, amount of work, and risks.
Step-by-step explanation:
The unit of measure used by the Scrum Team in estimating Product Backlog items is commonly referred to as Story Points. Story Points are an abstract measure of effort required to implement a Product Backlog item. Unlike traditional measures such as hours or days, which can be variable due to individual work speed or interruptions, Story Points provide a more consistent means to estimate work across different team members.
Story Points are assigned based on various factors including the complexity of the task, the amount of work to do, and any risks or unknowns associated with the item. The team estimates how many points represent the effort for a given task, with the scale being agreed upon by the team. This scale could be linear, like 1-10, or based on a sequence such as the Fibonacci sequence (1, 2, 3, 5, 8, etc.), which reflects the increasing uncertainty in estimating larger items.