There are two types of estimates when a team operates an agile framework like scrum:
Backlog-level estimates (high-level): They are used to quickly assess size and complexity and trigger discussions about what to do to assess risk and break large blocks into manageable ones.
Sprint-level estimates (low-level): They are used during the sprint to break down tasks and stories into sub-tasks and ensure the team agrees on how to tackle them, and the team will not overcommit.
Studies show that most teams have their best results using high-level and low-level estimates, called Full Scrum. Very experienced teams can sometimes only use high-level estimates without losing velocity or quality. This approach is called Light Scrum.
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