I am developing an app that will use the Twitter and Facebook login APIs exclusively.
Suppose a new user downloads the apps and is presented with the option to log in through Facebook or Twitter. The user chooses Facebook.
I think the procedure at this point is to
a) create an auto-generated user ID in my Users table
b) store the Facebook credentials against the auto-generated user ID
I am confused about part b. Does Facebook return a unique ID when their API is called that I can store against my user ID or is there some alternate process? In other words, what exactly does it mean to store the Facebook credentials?