The 2020 Scrum Guide defines an increment as ”a concrete stepping stone toward the product goal. Each Increment is additive to all prior Increments and thoroughly verified, ensuring that all Increments work together. To provide value, the Increment must be usable…The entire scrum team is accountable for creating a valuable, useful Increment for every Sprint”.

In scrum, a product increment is whatever you previously built, plus anything new you just finished in the latest sprint, all integrated, tested, and ready to be delivered or deployed. Without a usable product increment, development teams are delaying the delivery of value and are missing opportunities to get real user feedback and adapt the product to ensure customer satisfaction. On the other hand, incremental releases allow for fast feedback, quicker innovation, continuous improvement, rapid adaptation to change, and more delighted customers.

Sprints are the Scrum equivalent of an Agile iteration, which is a short period in which a team works to produce an end deliverable.

Within each sprint, there are Scrum inspect and adapt events, also known as ceremonies. These events or meetings are specifically designed to enable critical transparency and inspection.

There are four Scrum inspect and adapt events:

• Sprint Planning
• Daily Scrum (Daily Standup)
• Sprint Review
• Sprint Retrospective

Scrum events create an empirical behavior amongst teams if done in the right spirit. The Scrum Master should ensure the team understands each event's why what, and how. These events also help to create a flow of communication and provide transparency at every level.

Agile scrum artifacts are information that a scrum team and stakeholders use to detail the product being developed, actions to produce it, and the actions performed during the project. The main agile scrum artifacts are product backlog, sprint backlog, and increments.

The term artifact is often associated with archaeological ruins and ancient relics. Yet in software development, the term artifact refers to key information needed during the development of a product.

Agile scrum artifacts are information that a scrum team and stakeholders use to detail the product being developed, actions to produce it, and the actions performed during the project. These artifacts provide metadata points that give insight into the performance of a sprint. They are essential tools for every scrum team since they enable core scrum attributes of transparency, inspection, and adaption.

Product Backlog refinement is an ongoing process in which the Product Owner and the Development Team collaborate on reviewing and revising detail, estimates, and orders for items in the Product Backlog.

The Scrum Team decides how and when refinement is done. Refinement usually consumes no more than 10% of the capacity of the Development Team. However, Product Backlog items can be updated at any time by the Product Owner or at the Product Owner’s discretion. The Product Owner isn’t part of the Development Team and can invest as much time as necessary and enlist the help of other members of the Scrum Team.

The Scrum team can estimate either during product backlog refinement or during sprint planning events.
The objective of the Estimation would be to consider the User Stories for the Sprint by Priority and by the ability of the team to deliver during the Time Box of the Sprint.
Agile teams usually estimate effort using a metric called story points. Story points are the abstract value that takes into account the relative complexity and size of a task. Teams tend not to estimate based on person hours, but instead use Story points – a concept inherited from Extreme Programming (XP).