Developer Core Resource Library
The Developer Core Resource Library is a set of resources covering all the fundamental aspects of the Force.com platform and its various components, aimed at a developer audience. These resources will get you up to speed on the platform, providing all the necessary background and pointers to get you started developing applications and solutions quickly and efficiently.
This article provides a birds-eye view of the Force.com platform and its constituent parts.
The Apex programming language is used to code business logic, Visualforce controllers and triggers.
User interfaces can be constructed using Visualforce and Visualforce Components.
Persistence services are provided by the database, objects, relationships, fields, formulas and triggers.
There are many ways to integrate with the platform, including the SOAP API, outbound messages, email and HTTP/REST calls.
Packaging and Distribution
Applications can be packaged for distribution, and also listed on AppExchange.
Metadata and Force.com
The Metadata API and associated services provide the underpinnings of Force.com.
Force.com provides a number of security features, from infrastructure security through network, authentication and data sharing.
Tools for development and data manipulation include Force.com IDE, building with Force.com, Data Loader, and Migration Tool.