Facebook login API with non Meteor client

I’m building a mobile client natively (no Meteor) and using REST apis to communicate with my Meteor server. How can I use facebook login in a way that is consistent with accounts-facebook ?
What kind of token should I fetch on the client and what should I do on the server once the correct info has been passed from the client?

I think Facebook returns an access token but somehow Meteor also uses a secret token, and passes it with the fb access token to some method that in turn send some stuff to the server where I got lost (looking up login, which is the method name passed over the connection returns 15 pages of results on github…)