An action plan template is a means of developing a pathway to achieve a specific goal. Physical templates can be purchased or located on the Internet. Most are composed of Excel spreadsheets where you enter interim steps to achieve a particular goal.
A good template will provided a step_by_step approach with explanations as to why each step is proposed. The strength of the marketing plan derives from the integration of each step. So if you leave out a step, you may undermine your own plan.