An activation key, also known as a product key or license key, is a unique code required to activate and use a software product, in this case, Sketchcut Lite. The activation key verifies that the user has a legitimate copy of the software and allows them to access all its features.
Websites or reports claiming to offer free activation keys for paid software (or "pro" versions for free) often pose significant security risks: SketchCut PRO for Windows Sketchcut Lite Activation Key -FREE-