A task's code is a Liquid template. In the same way that a Shopify storefront might use a Liquid template to receive requests and render HTML, a task uses its Liquid code to receive events, and render a series of JSON objects. These JSON objects define actions, logs, and errors. (The work defined by these JSON objects does not begin until after the task has fully completed its rendering.)
Task code always has access to a set of environment variables, which can be used to make decisions about what JSON objects to render.
A task must purposefully consider its preview, so as to accurately communicate its intent to users and to the Mechanic platform.