About Plans
The Plans feature enables teams to easily plan their work into releases. Releases can be internal or external. For example, they might be iterations or milestones which are internal to the development organization, and releases that are provided to customers and users.
Plans are created only in the project scope. They are often hierarchical. For example, a Plan for a release named Version 1.1 might have several child Plans for iterations such as i21, i22, and i23. Teams can use any desired naming convention for their Plans.
Plan basics
The 
Plans topic in Navigation is the entry point to view and manage your release plans. Plans allow you to estimate work time, progress against each Plan, and can include multiple projects under a single Plan.
For each Plan, a team member or manager specifies the existing Work Items the team should complete between the Plan's start and end (due) dates. Estimated Work Items contain a value in the Initial Estimate field that indicates how long it takes to complete the item. The Plan aggregates and displays the total time of all initial estimates. The teams and managers then easily compare the estimated total time with the team's known capacity. For example, suppose the aggregated Initial Estimate for all the Work Items added to a Plan is 48 days and 6 hours (48d, 6h), and the period of the plan is 45 days (45d). Before work even begins, the team and managers can clearly see that the plan is overly ambitious and needs to be adjusted.
As work goes forward, charts in the Plan reflect the team's actual progress. Stakeholders clearly see at all times how much work is complete, and how much remains to be completed in terms of person days/hours. Teams and management are never left guessing about the probability of the Plan being completed by the planned Due Date. If progress is not what they originally expected, they can make intelligent decisions about adjusting the Plan, for example, removing some items from the Plan, or pushing the End Date forward.
By default, a Plan includes Work Items from one project. However, Plans can span multiple projects. For example, there might be separate projects for different components, all of which have the same release cycle. Therefore, Plans for iterations and/or releases need to include Work Items from all relevant projects. These projects can be specified in the Plan Properties.