A software that is designed to make sure that every member of a team has the same Local Version of an app. It manages Virtual Machines of different Operating Systems so that many different individuals can work together on the exact same codebase with the same tools and systems.

For instance, instead of just specifying the required Python packages, you can also specify the Operating System, Database, etc.

Note: (as of 2023-12-03 according to the startup note in the Docker Installation Guide) Docker Desktop is free for small businesses (fewer than 250 employees AND less than $10 million in annual revenue), personal use, education, and non-commercial open source projects. Otherwise, it requires a paid subscription for professional use. Paid subscriptions are also required for government entities.