#todo
Domain: A sphere of knowledge, influence, or activity. The subject area to which the user applies a program is the domain of the software.
- Eric Evans
The domain of an airline-booking program involves real people getting on real aircraft. The domain of an accounting program is money and finance. The domain of a source-code control system is software development itself.
Domain driven design, or DDD aims to model software based on the real-world system or process - the 'domain'.