When you add a package to a project manifest, Unity considers that package a dependency of the project. However, a package can also have dependencies on other packages, which might create indirect dependencies in a project that uses this package.
In this example, if you install Package A and Package B in your project, then your project has direct dependencies on both Package A and Package B. However, if Package B also has a dependency on Package C, then your project also has an indirect dependency on Package C.
A conflict exists when a project has dependencies on a package with different versions. A conflict can only exist between two indirect dependencies, when neither is added explicitly in the dependencies of the project’s manifest file.