Planning Center Online is a suite of separate applications that can work independantly to help you manage a specific need, or together to form a Church Management System. (Here's an article on why we believe in that strategy.)
If you are used to a different system, what you might refer to as modules are what we call apps, applications, or products. We call them that because although they can be used as part of a unified system, they are designed and developed independently, and each has its own pricing packages.
For more specific information about each of our apps, hover over any icon on our advertising page, or use the Product menu at the top to navigate right to it.