I would like know that , does it use web service API to map with the server ?
suppose, I already have an e-commerce website .I am gonna create an app for this website.My question how we fetch the data from that website, since we are not using any server-side scripts?
The client and server can be completely different technologies to each other - so your server side webApi is nothing to do with Ionic.
You would need to decide how to expose data from your web server - as a Microsoft programmer I use ASP.NET WebAPI - non-MS coders might use the LAMP or MEAN stack.
What is your website currently written in?
MEAN stack +1, (I am as a Microsoft programmer too )