Java Package
Java programs and programming interfaces( API) consist of collections of many individual files, each of which represents a class within object-oriented programming. In order to be able to give this class collection a structure and to improve thus the readability and usability for humans, Java packages were introduced.
It concerns a hierarchical structure, in which the classes (= files) are stored. Each package has a top level, in which arbitrarily many classes and further levels can lie. For each subordinate level again the same applies. Thus packages develop, which represent tree structures and make classes meaningfully addressable.