What does the mobile sign mean on fb chat?

[Axx]

I'm just curious to what it means as obviously the word 'web' means they're on their computer or whatever and the word 'mobile' means they're on their mobile so what does the sign mean? I know the sign with like 5mins' means they was last on 5mins ago but what does it mean when it's just the mobile sign?

[beercanz]

gas station is just ahead

[sunnys best friend]

They're using Facebook as an app on their mobe rather than using it on the Internet as a web page.