Your first model

A dbt model is just a SELECT saved as a file:

-- models/daily_revenue.sql
SELECT
  order_date,
  SUM(amount) AS revenue
FROM {{ ref('stg_orders') }}
GROUP BY order_date

Run it and dbt materializes the result as a table or view:

dbt run --select daily_revenue

ref() is the point: it wires models into a dependency graph, so dbt always builds upstream models first — your pipeline is the SQL plus its order, nothing more.