What the storefront controls•Which events are listed — only experiences that are listed on that storefront appear, including when data-experience-ids is set.
•The options offered by the filters (experience, category, language, location).
•Where the book buttons link to — each card links into that storefront’s domain.
If you leave it outUnderstory resolves a storefront for the company on its own. That is fine when a company has a single storefront — set the attribute explicitly whenever there is more than one, otherwise the widget may pick up settings and links from the wrong one.
Where to find the IDIn Backoffice under Storefronts → Implementation, the generated embed snippet already contains data-storefront-id for the storefront you pick. The ID is also the one in the URL while editing a storefront: /storefronts/<storefront-id>/edit.