There was a time when Viber used to be something that was only available for the iPhone. As time passed by, it also became available for other platforms. Right now, Skype and Viber are being used by different people in order to communicate with their loved ones. Skype is more used by people when they would like to do a video call. There are also some people who use it for their business when they want to coordinate and talk to different clients.
It seems that Viber right now is being used by people who would like to form groups. They may talk about different things when they are in varying Viber groups. The stickers in Viber are also updated constantly.