IPA - what 

I read the main page of the article on IPA.
On the plus side it is clear.
On the minus side, it makes no attempt to explain what the IPA is.  (context, scope, purpose, etc.)
Nice chart.  Lots of data (for people who probably have no need of it) but virtually no general information.
My questions (which weren't answered - keep in mind I'm a totally lay person):
An alphabet is used to 1.  Communicate between a writer and a reader (of the same language), 2.  Describe that communication (unambigously?)  Right?

Certain things are implied by its name, but clearly one should define what the subject of the alphabet is (are).  I have no idea if it covers all indoeuropean languages not to mention Mandarin Chinese (etc.)?
Does it (attempt) to cover all spoken languages? Written?  What about non-vocal languages (finger snaps - all that stuff).  Sign-language?  We now have some evidence that hand gestures are linked to language in the brain...but I digress.  From a simplistic point of view language can be thought of as being three distinct (context sensitive) types of communication: written/read, spoken/heard and performed/viewed.  I suppose an alphabet can't cover the last (but see how choreographers describe dance) and, obviously, there are non-alphabetical languages (pictographics, heiroglyphic, etc.) just as there are languages which make use of whistles, clicks.  SO what does the IPA do?

It just occured to me that maybe the IPA is (now-a-days) only used by euro-centric hobbyists and that would explain why there was no attention given to giving a serious explanation of what it is: "if you have to ask...{then you don't need to know}"