More information about the Product Backlog

To me, it seems like I have written several posts about the Product Backlog, but it is also true that the Product Backlog is a very important part of Scrum, and it is necessary to make sure that people understand all the details regarding what all Product Backlog is, how it is updated, when, who, and so on.
So, how is the Product Backlog used ? Well, given that the Product Backlog is supposed to be the repository of all the feature requirements and is owned by the Product Owner, it is one of the most important documents during the Sprint planning sessions. During the Sprint Planning meetings, the expected process is that the Product Owner attends the meeting accompanied by the Product Backlog, where the feature list is prioritized. The team then reviews the list, and decides the top items that they can accomplish by the end of the Sprint (and for a new item, this estimate of what they can accomplish can take some time to fine-tune; it is very much possible that the team initially could commit to too much, or too little).
In some cases, items need to get added on the Backlog through inputs from the engineering team, and these are typically architectural or design items that the Product Owner may not know about, or will have little idea; but they do need to get done, so they get added to the Product Backlog. In most cases, the prioritized items are selected, but there is some laxity if it turns out that some of the lower priority items are needed early for design purposes.