Active Record connects classes to relational database tables to establish an
almost zero-configuration persistence layer for applications. The library
provides a base class that, when subclassed, sets up a mapping between the new
class and an existing table in the database. In the context of an application,
these classes are commonly referred to as models. Models can also be connected
to other models; this is done by defining associations.
Active Record relies heavily on naming in that it uses class and association
names to establish mappings between respective database tables and foreign key
columns. Although these mappings can be defined explicitly, it's recommended to
follow naming conventions, especially when getting started with the library.