What are collections of classes that serve as building blocks for software development called?

The term used to describe collections of classes that serve as building blocks for software development is "class libraries." Class libraries provide pre-defined classes and functions that developers can use to perform common tasks, thereby saving time and effort in the software development process. By utilizing these libraries, developers can take advantage of already tested and optimized code, allowing them to focus on building the unique features of their applications without needing to write everything from scratch.

Frameworks, while also important in software development, provide a more comprehensive structure that includes not only classes but also guidelines and rules for building applications. They typically dictate the architecture of the project and contain built-in features that go beyond just a collection of classes.

Modules refer to separate files or units within a program that can contain classes and functions. They help in organizing code but do not inherently imply a collection of classes like a class library does.

Components usually refer to discrete parts of a software system that can be easily replaced or interact with other parts. While components can be made up of classes, they represent a broader concept in the software engineering domain that includes interfaces and the ways different software parts communicate with each other.

Thus, "class libraries" specifically captures the essence of the question by highlighting a structured collection of reusable classes designed to