Duplicate content is usually in the form of text and thus describes text passages (or complete pages) that can be called up under different URLs. In SEO, such duplicate content is not appreciated.
Search engines recognize that it is an internal copy and penalize the affected pages accordingly, since no added value is apparent from the duplication. Only unique content is considered valuable content. This is why it is particularly important in online marketing to always create new content and to link to existing content instead of copying it.