What does the online status on viber mean, is that the contact is msging/calling another viber contact or just that the app is activated in the phone and running un the back. B/c my contacts complain about me not replying to them even when im not using the app at all!

Does it mean that the contact is msging/calling another viber contact, or just that the app is activated in the phone and running in the background? My contacts complain about me not replying to them even when I'm not using the app at all!