Scrum artifacts

1.When is the sprint backlog created? 

This is covered extremely well in the Scrum Guide, which has a section on the Sprint Backlog. The Sprint Backlog is an output of Sprint Planning, which produces a Sprint Goal, a set of Product Backlog Items for the Sprint, and a plan for achieving the Sprint Goal.

There are a few key things that I've seen misunderstood.

First, accomplishing the Sprint Goal does not necessarily require completing all of the Product Backlog Items. Only some Product Backlog Items may be directly related to the Sprint Goal. The purpose of the Sprint Goal is to help the team make appropriate decisions and remain focused on ensuring the right work is done at the end of the Sprint to ensure added value to stakeholders.

Second, the Sprint Backlog is not locked down or finalized at Sprint Planning. The team needs to leave with some level of confidence that they can complete the goal and the specified work. Depending on the level of confidence desired and the risk acceptable, the work can be decomposed to varying degrees. Additional work may emerge throughout the Sprint, either by the team discovering what needs to happen to realize the Product Backlog Items and/or the Sprint Goal or by external events happening around the team. The Daily Scrum is a event for identifying what type of replanning or adjustment is necessary to maximize the chances of achieving the Sprint Goal.

In newer iterations of the Scrum Guide, the Sprint Backlog explicitly includes process improvements from previous Retrospectives. This is a relatively new addition to help the team focus not only on delivering value, but continuously improving the way they work to be more effective at delivering value.

2. When many scrum teams working on the same product,  should all the increments be implemented in every sprint?

If you have "many Scrum Teams", where "many" means 3 or more, you may want to look at various scaling frameworks. Options include Nexus, Large Scale Scrum (LeSS), and Scrum@Scale, which provide a method of explicitly scaling Scrum to multi-team environments. There are other frameworks that aren't as closely tied to Scrum, as well.

A common thread is that the teams, at the end of each Sprint, ensure that there is a fully integrated increment that is potentially releasable. Regardless of one or two teams, the output of a Sprint is a Product Increment that you can inspect, get feedback on, and adjust your priorities to continue to deliver valuable work.

Thanks Thomas for the detailed explanation. It really helped me in understanding about the scrum artifacts. 

Thanks,

Annie