Managing projects - IntelliJ IDEA in Action - page 141

4.6 Summary
Project configuration and management is an important aspect of software design,
and any worthy IDE provides functionality to address this need. Without it, an
engineer may as well be writing software in a plain text editor. The creators of IDEA
have invested much thought and effort into making the project-management fea-
ture set within their IDE support the needs of their audience.
IDEA uses the concepts of projects, modules, and libraries to decompose the
traditional concept of a software project. Projects are the highest level; they
equate roughly to the products you're trying to produce. Modules are wholly con-
tained subcomponents—individually buildable, runnable, and testable—that can
be assembled into a larger solution. Libraries are static modules that aren't
dynamically built or altered but that can be leveraged within the context of a
module. By defining these layers and making them self-contained and modular
(as Java components are touted to be), software designers can begin to reuse code
in multiple projects and also manage that task with a minimum of effort.