What is Open Source?

open source refers to a program in which the source code is available to the general public for use and/or modification from its original design free of charge, i.e., open. 
Open source code is typically created as a collaborative effort in which programmers improve upon the code and share the changes within the community.

Customer Relationship Management
Sugar CRM,Splendid CRM
Target
Contact
Lead---more known to you
User----customer,staff
List
Campaign---email,phone,web
Account---can be company or customer

A library is a collection of functions / objects that serves one particular purpose. you could use a library in a variety of projects.

An API (application programming interface) is a definition ('interface') of how to work with another application, system or technology. It essentially defines the operations that are available to interact with that other system. An API can be a library (meaning that the API is wrapped in a library or set of classes), but the distinction is that an API always references an external system - whether it's a database, web service, another application, or the operating system itself.

A Framework is a larger concept - it will normally contain a number of libraries and APIs to perform common tasks. It exists on a higher conceptual level - it's not just a collection of tools, but also a collection of design patterns, best practices, and methodologies. A software Framework is an extension of a a general framework - its meanings include being a foundation from which things are built, providing support and structure, and giving guidance and definition to requirements.