Help me understand. Do apps like Whatsapp and Snapchat help spread information publicly but also in private?

Both apps as far as I know use chatgroups which can open communication between hundreds of individuals can they not? And people outside the app cannot access these private groups so what information is shared is shared privately but then can be spread to more of these groups if users belong to more than one. This begs the question of whether something can 'go viral' and have a public impact yet still be private?

I ask this because I have …

apps information privacy snapchat whatsapp