Product Backlog refers to the list of tasks that are decomposed according to initial requirements, including all functional and non-functional functions. The product owner determines the priority level for the tasks in product backlog, when a development team starts a task, it precisely defines and breaks down the task.
Product backlog is the general outline of all functions required by the product. At the beginning of a project, no one was able to anticipate all the tasks and needs in advance and develop a full, detailed and all-encompassing plan for it. The feasible method is to first write down all the notable features and functions of a project. The number of features does not need to be large, so that the first sprint of the team can work properly.
As the sprint progresses, the number of product increments that can be released increases, and the customer's intuitive understanding of the product increases accordingly. They can recommend that you change or add tasks in the product backlog accordingly.
At the Sprint plan meeting, the product owner determines the priority for the tasks in the product backlog and describes the tasks to the scrum team. The SCRUM team then, based on the overall situation of the team, determined what features they could accomplish in the upcoming sprint and moved them to the sprint backlog.