Sprint planning is a meeting held between the Product Owner and the team doing the work. The Product Owner is the one that prioritises the backlog and also briefs the team on the items at the top of the backlog.
The team then estimates the backlog items and because it knows its typical sprint capacity (i.e. its velocity) it decides how far down the backlog it can go. For example, it might have a velocity of 20 points and so would select the items prioritised by the Product Owner down to the point where they had roughly 20 points allocated.
Scrum doesn't really prescribe much beyond that point up until the end of the sprint and the sprint review. Its up to the team and the Product Owner to agree on how they will work.
With most teams the process would be as follows. The team would work on the items allocated to the sprint, roughly following the prioritisation used by the Product Owner. They may vary the order a bit from the Product Owner's priorities for technical reasons. All along there would be constant communication between the team and the Product Owner. The team would ask frequent questions, seeking clarification on the stories allocated to the sprint. They will often also demonstrate progress to the Product Owner to get their feedback.
Reporting is not usually done in a formal way as Scrum is set up to be highly transparent. The main forms of reporting are the task board, which acts as an information radiator, and the daily stand-ups that non-team members can attend (but not interrupt) and get a feel for what is going on.
Remember that agile encourages communication and interaction over process. As there is much interaction between the team and the Product Owner there is rarely any need for other reporting tools.
There is no obligation on the team to complete the work allocated to the sprint. Instead, they work their way through the items as best they can and striving to achieve an agreed definition of 'done' for each item. If there are stories incomplete at the end of the sprint they do not count towards the measurement of the team's velocity. That way the actual rate of progress is used to drive the team's capacity planning. The intention being to achieve a sustainable pace that maintains quality.