prompted me to ask this.
The answer can be found quite easy in the Wikipedia article about GitHub.
Now, I could have copypasted the introduction to the Wikipedia article (linked, and with proper attribution), and probably picked up some cheap experience points in the process.
But I've seen this before (a string of questions and answers copied verbatim from the FSF FAQ from a user that has since departed comes to mind). I feel that very general questions where the answer can be found in a Wikipedia article, an obvious FAQ, etc. should be considered off-topic if that is all there is to the question. I find it hard to believe that the askers of these do not know about such resources. Hence I regard these types of questions as a covert way to request (links to) such external resources. We already say requesting external resources is off-topic.
Questions about specific problems where the answer can be supported by reference to external resources (including Wikipedia and FAQs) should however be welcome.
(1) Just to make my intent clear. My criterion for closure is not "too easy to answer" - I believe that easy to answer questions should be welcome here. But i think it is off-topic because both question and answer is too generic. If the answer will be nothing more than a link to, or quote from, an external resource, then the question should be considered off-topic.
(2) This is not a duplicate of Are FAQs on-topic? Please note that the question that started that discussion was not an invitation to copypaste a couple of quotes. It you look at the upvoted and accepted answer, you'll find it is has carefully curated several quotes by putting them in a context that may have eluded somebody just using Google to locate the quotes. Such questions are clearly on-topic. It is general questions that can be answered without doing any significant curation or explanation of the quotes it shows I want to see closed.
However, this is related to (but not a duplicate of): Should we copy questions from the GNU GPL FAQ as that was specifically about questions that could be answered in full with single questions from the FSF FAQ. This question is in a similar vein, but has a wider scope than the FSF FAQ.
Please note that the main answers of Should we copy questions from the GNU GPL FAQ and Are FAQs on-topic? goes in the opposite direction. This indicates that these are different questions, not duplicates.