for managing attributes and their values
to create a simple data class
to create a simple DTO (Data Transfer Object)
defines a set of attributes to hold values, and defines their accessor methods (getters and setters; readers and writers)

Person = Struct.new( :firstname, :lastname, :age )
# creating a new subclass of the class Struct
# this subclass is assigned to the constant Person
# when a class is assigned to a constant, then in general Ruby creates a class with the name of this constant (Person)
# now Person is a class

person = Person.new( 'Tom', 'Sawyer', 11 )

person.firstname   # => Tom           # getter, reader
person.lastname    # => Sawyer
person.age         # => 11

person.age = 12                       # setter, writer

person.age         # => 12

person.inspect     # => #<struct firstname="Tom", lastname="Sawyer", age=12>

person.members     # => [:firstname, :lastname, :age]     # returns it's members (attributes) as an array
person.values      # => ["Tom", "Sawyer", 12]             # returns the values of it's attributes as an array
                   
person.class       # => Person
Person.superclass  # => Struct