Also, smartthings is in the middle of a major transition: new hub, new app, new cloud.
The old cloud ran custom code that was written in groovy, as well as almost all of the official functions. More on that in the following FAQ,
The new cloud will not allow individual developers to upload code. Instead the developer has to host it themselves somewhere else and access smartthings via an API. No more groovy. For information on that, see the developers page:
The ADT panel does have some functions that it runs locally which are different from the home automation options, but we as customers don’t have any access to those. They’re just to support the built-in security monitoring features.