Profile is like the canopy of a forest. It's the highest level view of your client's information and it's all encompassing. As you work your way down from this high vantage point, certain goals, accounts, income, and other information flow into the plans you create. A plan may be as specific as funding a child's undergraduate education or more sweeping like retirement and charity planning. Overall, profile information is real existing client details whereas a plan is a scenario that you create so that you can run a Monte Carlo analysis.
When you are creating a new Plan, you begin by pulling over the relevant goals, accounts, and income that you had previously created in Profile. From there, you apply your asset allocation models and your tax assumptions. The timeline of any plan is dictated by the goals that are attached to that plan. That means that the start date is the current year, and the end date is the latest date of all the goals that you've attached to the plan.
Since a Plan is really just one big simulated scenario and you want to test different perspectives, you can create different hypothetical scenario Goals, Accounts, and Incomes. When you do that, those scenario items are only pushed up to Profile when you decide it's the right thing to do, make the appropriate real life changes, and it becomes actual existing data.