As previously stated, models are a means of abstracting and giving a common interface to data. In most web applications, data is stored and retrieved from a Relational Database Management System (RDBMS), which is a database that holds data in a tabular format with rows and columns and is able to compare data across tables. Some examples include MySQL, Postgres, Oracle, and MSSQL.

In order to create models on top of our database, we will use a Python package named SQLAlchemy. SQLAlchemy is a database API at its lowest level and performs Object Relational Mapping (ORM) at its highest level. An ORM is a technique to pass and convert data between two sources with different types of systems and data structures. In this case, it converts data between the large amount of types in databases versus the mix of types and objects in Python. Also, a programming language such as Python allows you to have different objects that hold references to each other, and...