Parameters are a set of static, named metadata about a story, used to control the behavior or appearance of components within Storybook. They can be set globally to affect all stories or locally to affect individual stories.

Storybook doesn’t do a lot with parameters out of the box, but they’re particularly helpful when working with addons. You can define parameters at a bunch of different levels:

• .storybook/preview.ts: These parameters are globally available to all stories.
• In the Meta for a set of stories.
• Scoped to a particular story.

Along the way, parameter objects are merged, so your individual stories will inherit parameters defined at a higher level, but they can also override those parameters if needed.

The important part here is that parameters can be accessed by decorators and controlled using addons. This allows for a ton of flexibility for adding custom functionality to control your stories.