A plan is typically any diagram or list of steps with details of timing and resources, used to achieve an objective to do something. It is commonly understood as a temporal set of intended actions through which one expects to achieve a goal.

For spatial or planar topologic or topographic sets see map.

Plans can be formal or informal:

• Structured and formal plans, used by multiple people, are more likely to occur in projects, diplomacy, careers, economic development, military campaigns, combat, sports, games, or in the conduct of other business. In most cases, the absence of a well-laid plan can have adverse effects: for example, a non-robust project plan can cost the organization time and money.
• Informal or ad hoc plans are created by individuals in all of their pursuits.

The most popular ways to describe plans are by their breadth, time frame, and specificity; however, these planning classifications are not independent of one another. For instance, there is a close relationship between the short- and long-term categories and the strategic and operational categories.

It is common for less formal plans to be created as abstract ideas, and remain in that form as they are maintained and put to use. More formal plans as used for business and military purposes, while initially created with and as an abstract thought, are likely to be written down, drawn up or otherwise stored in a form that is accessible to multiple people across time and space. This allows more reliable collaboration in the execution of the plan.