@pjreijiri for resources to start with, please refer the link http://help.autodesk.com/view/fusion360/ENU/?guid=GUID-A92A4B10-3781-4925-94C6-47DA85A4F65A .
The same link can be accessed from Fusion application through Help >> Learning and Documentation >> Fusion 360 API.
It contains loads of data to work on Fusion API's. It also has videos for easy understanding.
To understand the difference between scripts and add-in refer to the topic 'Scripts vs. Add-Ins' in the link http://help.autodesk.com/view/fusion360/ENU/?guid=GUID-9701BBA7-EC0E-4016-A9C8-964AA4838954
Regards,
Rushikesh Kadam.
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Rushikesh Kadam
Senior QA Engineer
Quality Assurance
Autodesk, Inc.