Convention over Configuration means Rails assumes what you want from standard names and places, so you write configuration only when you break a convention. Some of those conventions:
The model User maps to the database table users.
The controller UsersController handles the /users routes.
Every primary key is named id.
A foreign key is the singular table name plus _id, like user_id.
Following them means less code to write, and every Rails project looks familiar to a new developer.
Rewriting in plainer words…
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