Online community users know the XY problem:
A person has a problem X and tries to solve it with Y. He asks about help with Y online.
Often X has a straight forward solution which is not Y. But the person asking doesn't describe X.1
The term "XY problem" was implicitly coined when the Open Source philosopher Eric S. Raymond wrote his "How To Ask Questions The Smart Way" text and added "How can I use X to do Y?" to the "Questions Not To Ask" section.
ESR himself states in "How To Ask Questions The Smart Way":
Describe the problem's symptoms, not your guesses
It's not useful to tell hackers what you think is causing your problem. (If your diagnostic theories were such hot stuff, would you be consulting others for help?) So, make sure you're telling them the raw symptoms of what goes wrong, rather than your interpretations and theories. Let them do the interpretation and diagnosis. If you feel it's important to state your guess, clearly label it as such and describe why that answer isn't working for you.
Since the preceding point seems to be a tough one for many people to grasp, here's a phrase to remind you: "All diagnosticians are from Missouri." That US state's official motto is "Show me" (earned in 1899, when Congressman Willard D. Vandiver said "I come from a country that raises corn and cotton and cockleburs and Democrats, and frothy eloquence neither convinces nor satisfies me. I'm from Missouri. You've got to show me.") In diagnosticians' case, it's not a matter of skepticism, but rather a literal, functional need to see whatever is as close as possible to the same raw evidence that you see, rather than your surmises and summaries. Show us.
As online communities like IRC or forums are quite aware of the XY problem now, the people involved will often quickly focus on getting behind the issue presented. They will ask questions around the "why" do you want to do Y, what is the reason for you seeking help on Y etc. trying to uncover X.
They have been trained by numerous long winded discussions of why somebody would want to solve something as awkward as Y which slowly lead to uncover the unarticulated underlying problems X.2
There are many alternate definitions for the XY problem available on PerlMonks. Some - like ESR - define Y to be the original problem and X the offered solution. I stuck with Greg Wooledge and John D. Porter and used X to be the underlying problem and Y the exposed question or request. That occurs more intuitively to me and seems to be the more frequent definition. As they don't change the message both nomenclatures are fine and time will tell which one prevails. ↩