Entities
There are two kinds of objects that represent things, entities and value objects. Entities are objects with an unique identity, such as Nellie or David's car, while value objects are objects that we use for their values, such as five or green.
In Java, java.io.File objects are value objects. They represent
paths (absolute or relative) in the file system. Any number of File
objects may reference the same path. The path that a File
object references may or may not contain a file. If a file referenced by a
File object moves away and
someone puts a directory there instead, it is still referenced by the same
File object. If the directory is deleted and a file is put there
again, the File object is still valid. The part of the application
that holds the File object may be totally unaware of what has
happened and, worse, may still assume that the File object still
references the original file.
In EntityFS, file system entities (files and directories, mostly) are treated
as entities. Only one org.entityfs.EFile object instance may reference a
file in the file system. If, for instance, another part of an application
wants to use the same file, it uses the same EFile instance. If
it moves the file, the same EFile still represents the file,
and it is updated with the file's new location. Everyone that uses that
EFile object will see what has happened and can respond to that
if they want to.
You can read more on this in the Architecture overview. An excellent book on the subject is Domain Driven Design by Eric Evans.