Alan MistêThe #fields of an #object are all the #DataVariables that make up that object. They are also sometimes referred to as #attributes or member variables. These fields are usually made up of #primitive types like integers or characters, but they can also be objects themselves.
For example a "book" object may contain fields like title, "author" and "numberOfPages". Then a "library" object may contain a field named "books" that will store all book objects in an array.