Apple Support Communities is a section of the Apple web-site which connects Apple users all over the world. Through this let’s call it ‘help engine’ you can share your problems that you are experiencing with the product you own and get troubleshoot solutions from other users.
I believe it to be quite helpful, because you are able to help other Apple users if they are experiencing a problem, you can give advice on better work with an iPhone for example etc. From personal experience I know this community to be extremely useful, because me as an Apple user have encountered several issues with my products and through ASC I have managed to fix them.
Sometimes it can be tricky, because the issue you are having with your product may not be resolved by other people or you would need to contact Apple Support itself. Though this happens, it is perfect for small problems and really helpful to new users. I definitely recommend it.