A dependency is software that a project relies on to do some of its work. It might be a library that helps display a chart or a tool that checks the code.
Imagine a person building a desk using screws and hinges made by someone else. The desk depends on those parts being available and fitting correctly.
Dependencies can save time, but they also need care: teams should know what they include and update them when necessary. If a dependency changes or becomes unavailable, parts of the project may need attention.