Norm from MS has a great post about what happens where in PPS and Sharepoint:
“Microsoft has several business intelligence (BI) tools that seemingly overlap in features. This can be confusing to those trying to determine what BI tools will be most beneficial to their company. Many software packages have added an element of business intelligence -tools that lend to better business decisions. The reason for the addition of BI tools extends to acquisitions Microsoft has made. An example is the acquisition of ProClarity, a powerful analytics application platform that is included in the PerformancePoint Server (PPS) license agreement. Additionally, as BI has become more available with the increase of data warehouses technologies, improvements to ETL practices, and reporting, software packages (particularly accounting and Excel based) have been able to add elements of BI.
To resolve some confusion between Office SharePoint and PerformancePoint Server BI features, I have created a chart that shows how each tool can effectively monitor, analyze, plan (forecast), and report for the information you need to achieve corporate objectives. “