Magento knowledge center
The Magento team provides great resources of documentation in order to increase the Magento developer's knowledge.
In the Magento documentation (http://magento.com/help/documentation), the user can access the USER GUIDES section for ENTERPRISE EDITION, COMMUNITY EDITION, DESIGNER'S GUIDE, and DEVELOPER DOCUMENTATION.
I strongly suggest that you, dear reader, study Magento's COMMUNITY EDITION, DESIGNER'S GUIDE, and DEVELOPER DOCUMENTATION in the first instance. These three documentations have solid concepts, and you can certainly take advantage by building your Magento concepts.