Models, databases, and relationship questions

What is a primary key?
 * The id of a resource in this table.
What is a foreign key?
 * The primary key from another table used as a link to find data. 
Why would one row of data have both primary and foreign keys?
 * If it was a join table or if the table had a one to many relationship.
What is Rails' convention for the column name of the primary key?
 * id
What is Rails' convention for the column name of a foreign key?
 * singular-table-name_id
What are dev, test, and prod databases all about?
 * They are seperate enviroments. One for testing , another for development, and a final for the production code.
What is the database.yml and how is it used?
 * It shows all of the enviroments that were created (test, development, production)