The choice component allows you to semantically group multiple components but only allowing one to be used at the time. This enables polymorphic components when editing the content, e.g. being able to choose if a hero component is image, video or even a relation to a richer media item.
Semantic structure with flexible shapes
The concept behind the choice structural component is that you can define shapes that give choices to the editorial user to e.g. manage different types of hero media like the image, video or relation example below. This still keeps semantic integrity with all choices being grouped as hero, but the editorial use can only select one when creating the item.
Editorial flexibility with choice component
When writing your product information there will be different sets of properties that describe a TV vs a fridge. When selected by the editorial user you both get the information about what type of product it is, in addition to having specific properties describing the TV or the fridge.
Flexibility while still retaining semantic structures for your product information and content.