Wh-something refers to interrogative words.
The 'wh' refers to the fact that in English most of them start with wh: what, where, whence, where, whose.
Interrogative determiners include words like which, what, and whose.
Interrogative pronouns such as that, what, whatsoever, and which.
Interrogative adverbs include things like how, why, and also wherein and however.
It can be seen as a subcategory, applying to various lexical categories. In writing you may abbreviate, for example, interrogative determiners to 'Wh-determiners.'