What exactly is a framework? How to define a framework in simple terms?
A software framework, in computer programming, is an abstraction in which common code providing generic functionality can be selectively overridden or specialized by user code providing specific functionality. Frameworks are a special case of software libraries in that they are reusable abstractions of code wrapped in a well-defined Application programming interface (API), yet they contain some key distinguishing features that separate them from normal libraries.
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I think framework is a piece of software, libraries, utilities and documentation to restrict some software development cycle by imposing some design standardization like to modularize component models for re-usability, scalability and maintainability.
If the interviewer is looking for a proper definition of a framework, then the job is not very desirable. If, though, the interviewer is interested in your level of experience, and whether you have a sense of what sorts of problems the various popular frameworks attempt to solve, then you won't be helped by being prepared with a slick definition.
Interviews are stressful, but if you put your energy into improving as a software developer, you will become the candidate that is attractive to the right sorts of companies.
Framework would typically have some sort of "inversion of control" so that the framework code calls the application code at specific places so that the application code completes the framework, whereas library API would just be invoked from the application, not the other way around
System
If you don't know what it is, call it a system.
Module
If you don't know what it does, call it a module.
I don't know when to call a thing a framework though :-(