The CreaTools software is a framework for both end-users and developers. It provides on the one hand ready-to-use medical image processing applications and on the other hand components, libraries and a development/execution framework allowing you to create your own applications. This is a very simplistic representation of the system:

End-users, the ready-to-use applications (image tools) will give you the possibility to visualize images, filter them or contour regions of interests with only a few clicks.
Developers, using the developer tools and the existing libraries you can