[We follow Biber (1989) in using text type as a generic term for the many ways in which a text might be classified.]
a text type refers to values assigned to structures (e.g. documents, paragraphs, sentences and others) inside a corpus. Text types are sometimes called metadata or header information. Text types can refer to the source (newspaper, book etc.), medium (spoken, written), time (year, century) or any other type of information about the text. Not all corpora have documents annotated for text types. Corpora can be divided into subcorpora based on text types and searches and other analysis can be performed only on texts belonging to the selected text type.
The text type selector is used to limit the analysis to only certain text types.
Users can include metadata into their corpora. If the metadata are in the required format, they will be converted to text types and will appear in the text type selector.