Where do I find the minimum requirements for an app? I was trying to install a new app from Google Play on my computer, but a message told me that the app wasn't compatible with my device. No more information was given.

Can someone please tell me where I can find the minimum requirements for any given app? I want to check what's missing on my phone. Maybe I can fix the problem, assuming it isn't a hardware problem.
The theory is that you should not need to know.  When the developer publishes an app there is a manifest.xml file that describes the required capabilities.  These can be both hardware and firmware related.  e.g. you need a minimum Android version or you need a specific hardware feature like GPS.  Google Play then automatically filters which apps you can see and install based on these requirements.  The developer can also impose geographic requirements and potentially carrier requirements as well as disallowing specific devices if they want to.

In your case the obvious thing to do is to first check if the developer has a website with any more information.  If that's of no help try emailing them  the filtering can be tricky and catches developers out.  If the developer is at all responsive they should come back to you.  It is in their interest to have the app work on as many devices as possible normally, so if there is no good reason for it to be incompatible with your device they should appreciate the opportunity to work out the issue.  If there is a valid issue then your question may help prompt them to make the information available on a website or in the description.