What and for how long additional OR separate benefits I receive after buying Apple Care?

I bought a MBA 13" in India (home) last month.
I wanted to know about Apple Care / Extended warranty that is available for sth like ~15K (INR).
Can you please give me a detail as in what do I get with this for my Mac and for how long?
Can I buy this before the day my current/default warranty expires or shall I have to buy this within some stipulated period from the day of purchase of my Mac?
What is already available for my Mac as of now and for how long? Shall anything be added to warranty or care that is available with my Mac as of now? Shall be added right from the day I buy it or it will happen so after my current warranty/care gets used up i.e. after completion or 1 year or for whatever period MBAs comes with care/warranty. So, these extended warranty simply increases the number of years on my protection plan or gives additional cookies?
If I buy an iPhone5 then shall I have to purchase separate apple care for that? Or is it available for all my Apple products? Or if not then are there such plans that I can buy to cover all or many of my apple products and are cheaper as a combined purchase?
Within that period if let's say my Keypad fails screen goes kaput then Apple will either fix it/replace it or it will ask for extra money if it needs replacement? Or will ask for extra money even if it was not accidental damage (my fault)? I read sth about accidental damage with AppleCare purchase - it adds to the first year also or only during the next two years (or next 3 years - not sure how long it holds).
Shall I have to buy it offline or i can buy it online too? What if I buy from another country (online/offline) if it's available for cheap over there?
I see some deals on such packages on eBay - mostly on USA eBay, and have read posts people buying it but they were mostly from USA/EU. Can I buy one of those? Shall they be valid for my product(s)?
By the way, does Apple provide an email support with those plans because I couldn't find one email address for Apple support.