Android : How to feed data to a mobile app for a website

There are various websites (say LinkedIn) which have a corresponding mobile app.My question is - "How they feed data to their mobile apps?". Obviously they are not doing HTML scraping of their webpages, otherwise it would be really inefficient.

I am asking this because I have a website, and I am also going to develop an android app for that.So, do I have to design my website (like database) in a specific way to support mobile apps. (I mean, what are the preconditions do I take care of , while designing my website, in relation to the mobile apps)