A backlog is part of the scrum method. It's a list of uncompleted work or matters needing to be dealt with. There are two types of backlogs: a Product Backlog and a Sprint Backlog. A product backlog includes all tasks that need to be dealt with to complete the product. It's a list of all the user stories, prioritised by the Product Owner. A sprint backlog includes all tasks/user stories that need to be dealt with in a particular sprint.

You can have a look at the top of the Product Backlog to see what will be our focus in the next sprint