Project progress should be visible and measurable in order to be useful. In addition to the three scrum artifacts (product backlog, sprint backlog and the increment), agile project teams often use three additional artifacts (product vision statement, product roadmap and release plan) to enhance their effectiveness. These artifacts provide both strategic and tactical direction to the team as well as radiate project progress to the organization.
Product vision statement
The vision statement is the elevator pitch to communicate the product's end goal (not what it currently is, but what you want it to become) in terms of differentiation, competition and how it supports the organization's overall strategy. The product vision provides the outermost boundary of what is considered part of the project.
The product roadmap is a holistic view of the high level functionality required to achieve the product vision, and provides the "big picture" view teams need to stay focused on the vision. The product roadmap is the initial cut at the product backlog (see below).
The release plan outlines the next set of functionality from the product roadmap the product owner deems valuable to release to the marketplace. The release goal establishes the mid-term boundary around specific functionality that will be released to customers to use in the real-world.
The product backlog is an ordered to-do list of all the requirements for developing the functionality to achieve the product vision, prioritized by business value and risk. The product backlog provides more detail than the product roadmap and defines the scope of the project. Since the product backlog is an ordered list, the items near the top are higher priority than those at the bottom. Since it is more likely the items at the top will be developed than the items towards the bottom, product backlog items will increase in detail and refinement the higher in the list they appear.
The sprint backlog is a list of the tasks required for a scrum team to create potentially shippable functionality in support of a sprint goal. The sprint backlog is one of the three scrum artifacts, and often includes a sprint burndown chart, which gives daily visibility to the project team whether the team is on track to meet its sprint goal. Each sprint goal supports the release goal, and establishes the immediate boundary that allows the team to commit to the amount of work that will be accomplished that sprint.
The increment is fully developed, working, potentially-shippable functionality at the end of each sprint. Although the product owner doesn't have to release every increment to the customer at the end of every sprint, the product owner at least knows each increment is ready to release to the marketplace once there is enough aggregated value.