update faq

docs/source/faq.rst

@@ -15,9 +15,20 @@ General Questions
 *What is "Birdhouse"?*
 ----------------------
 
-*Birdhouse* is collection of Python packages to make the usage of Web Processing Services easy.
+*Birdhouse* is collection of Python packages to make the usage of Web Processing Services (WPS) easy.
 The available packages are used in the climate science community.
 
+*What is "WPS"?*
+----------------
+
+The very short answer: 
+
+WPS is the acronym for Web Processing Service.
+
+The sligthly longer answer:
+
+So, let's say you have a function (maybe written in Python) which might calculate the "summer days in finland since 1990". Then this function has probably input parameters (region, from-date, to-date, NetCDF files, ...) and an output (or even more ...) which might be just a interger number or a text document or even a diagram. Now, you would like to provide this function as a web service, so that other people can call it with just a simpel URL like http://myhost/wps/identifier=summer_days&region=finland ... ok ... then you should have a deeper look at this WPS thing  ... 
+
 Getting Help
 ============