Artikel – on the German articles *der, die, das, ein* (and their declensions). Do not use for question about finding out the grammatical gender of something.
You should use this tag if your question is targeting the definite article der/die/das and its declension forms or the indefinite article ein and its declension forms.
As the article indicates grammatical gender, questions about determining the right article are often actually questions about determining the right gender. In this case, use gender instead of this tag.