Product backlog contains features and stories to be implemented.
Product backlog is a list of all things that needs to be done within the project. It replaces the traditional requirements specification artifacts.
As per https://www.scrum-institute.org
Each Scrum Product Backlog has certain properties that differentiate it from a simple to-do list:
The backlog has to be managed carefully. During initial setup, Scrum Team and its Scrum Product Owner start by writing down everything they can think of easily. After this initial setup, the Scrum Product Backlog has to be maintained in an ongoing process that comprises the following steps: