Which questions does this tag cover?
A good example question is understanding "virtual memory", getting to understand something is key to being able to solve problems related to that subject. homework is about these types of questions.
A bad example question is please make this Unix assignment for me, we do require people to (ironically) do their homework before asking a question about their homework. We're not here to solve your assignment, but merely to give you explanation or advice on doing so. Don't ask how to do X, instead try to ask what you need to know in order to do X; the key is asking for advice and explanations.
Is this tag allowed to be used?
Because it isn't clearly disallowed under the rules, and it's controversial, it is allowed on Stack Exchange.
Jeff Atwood notes the usefulness of the tag, and shows further in his answer how it meets the rules:
Homework, I am torn on, because although semi-meta, the tag does tell me with a fairly high probability what the question is likely to contain, and that it's a student who asked the question.
And Diago, a former mode, confirmed that view on our meta. And adds very useful links:
The [homework] tag is one of the few meta tags still allowed since we welcome homework question on the Trilogy. More on the [homework] tag on MSO here. More on the homework topic on MSO here.
