How does someone become a user of my application?

I'm trying to learn how to use the realtime update API. As far as I understand, if I create a subscription for my application to the object type "user", I will get an update whenever a user of my application changes one of the specified fields.

So the questuon is: Who is 开发者_开发知识库a user of my application? When does one become my application's user? Is it when he/she uses it the first time? Is it when he/she installs it? Do I get updates only if the changes happen while the user is logged in? Etc.

I'd like to understant the exact answer in each of the following cases: - a Website - a native or desktop app - an app on facebook - a page tab

I can't find any of this explained in the Documentation.

Thanks in advance m.

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it is when he/she installs it. when it change something on facebook profile, your url will be pinged(you must set in app settings) take a read here http://developers.facebook.com/docs/reference/api/realtime/