Package Manager vs Dependency Manager

Question

What are the differences?

In many places they used interchangeably as synonyms but I think they are different. What is the key difference in short?

Answer 1

There is an excellent and simple explanation on Composer's website:

Composer is not a package manager in the same sense as Yum or Apt are. Yes, it deals with "packages" or libraries, but it manages them on a per-project basis, installing them in a directory (e.g. vendor) inside your project. By default it does not install anything globally. Thus, it is a dependency manager.