Do I show up as "online" even when my WhatsApp app is closed?

Hello,
I'm wondering if I have whatsapp installed on my android cell phone but not running, meaning it doesn't show up when I press the recent apps button on my phone, will I show up as "online" to other whatsapp users in my contact list? I ask because a few days ago, a friend sent me a message asking me if I was available because she said she could see that I was online. However, I'm almost certain that I had ended the app about an hour earlier (tapped recent apps key then tapped the X on whatsapp. Also, let's say I do have whatsapp running but I'm using another app for example twitter, would I show up as online then? I'm assuming so considering I have the app open but want to be sure.